This is so difficult.
Your partner has proven herself to be untrustworthy, regardless of her reasons.
I think if there's any way of making this work, there has to be a new approach taken.
It seems that your partner is not good at expressing her needs. She doesn't put them out on the table, she just goes off and fills them. Impulsivity, exhaustion, immaturity, it could be a number of reasons.
How can you get to a point where she will tell you these things? Well... this event has happened and now you can either both pull away and admit a lack of current compatibility... or you can try to discuss new ways of approaching these problems.
What happens when your girlfriend tells you how she's feeling? Does she tell you? Is she more used to being the 'fixer' and listening to your issues? Can she learn how to communicate better? Can you learn to listen better, if you don't currently?
Anxiety is a very difficult one. As you say, it needs to be worked on from within.
Even the most secure person can feel insecure about their relationship, for very valid reasons. In those circumstances, reassurance from the partner helps.
Sometimes, when we talk about issues, we make them bigger than they are. I'm a Psychologist and a talker.. ~grins~ ... if I have a problem, my immediate urge is to tell my partner, my best friend, anyone who'll listen.
But when does that become a vicious circle?
Ok, let's take this as an example.
I have demons when my girlfriend goes out on a date, especially with someone new. I definitely have feelings - I'm not a poly robot.
In the beginning, I would talk to her about every little feeling and she would tell me about every little feeling she had.
It became this big ball of stress and feeling. Even when she was feeling good about something, I'd feel bad because she was feeling good. And I'd tell her that. And she'd tell me that.
It sounds to me that you need another outlet, so that your problems and anxieties aren't going over and over. This is a good place for that
You could even start your own blog here, in the life stories section, if you think it would help.
I'm definitely not saying "don't communicate with your partner". But everyone has a limit. I'm definitely not saying that you're "too" needy, "too" anxious, etc.
What does concern me is the compatibility of the two of you. Everyone is different.
I have a lot of patience. My girlfriend doesn't. I'm used to dealing with people's stress - my girlfriend gets stressed very easily. I have a high moral code when it comes to our relationship - she is sometimes more easily swayed by her individual wants and needs.
At times, I've doubted our compatibility. Sometimes I think to myself that I'd prefer someone more patient and understanding. But for now, I'm very happy and hope that we continue to teach each other different ways of being.
However, it does mean that I've considered ending, or changing the relationship.
You need someone patient, understanding and who sticks to their word. Your girlfriend's end of the deal is that if she agrees to a guideline, she's got to stick to it! We all make mistakes, but she should own up to them if she makes them.
I truly cannot tell you what to do, because we are only seeing your relationship from the small window of a few paragraphs. It does strike me that you are not getting what you currently need from her; nor her from you. And because of that, I do wonder if a less 'primary' relationship would do you both some good... or even to consider a trial separation.
Failing that, I think it's going to take a lot of talking and both of you being very clear. Get your expectations out there. What are they? Try making a list and going through that with her. Get her to do the same. Be really black and white at first and see where that takes you.
It could be things like:
(you) - I expect you to stick to guidelines and tell me straight away if you make a mistake
(her) - I expect softer guidelines - I cannot stick to these
(compromise) - guidelines remain the same, but she's honest when she misses them... or guidelines soften and she's still honest
(her) - I expect to sleep with other people in the future
(you) - I'm not able to deal with that right now
(compromise) - 6 months from now, I would like us to review this again, until then, no dating for either of us
(you) - I need you to understand my anxiety and my insecurity, as well as my need to talk
(her) - I need you to let me rest sometimes; I need you to accept and understand that you leave me feeling swamped
(compromise) - I will try to work on the 0-2 level stressors alone and only come to you with the 3 and above. We will discuss 4-5 stressors before they happen, where possible. You must also let me know when your listening tank is running on empty.
Well, there's a difference between communication and constructive communication. God knows, I'm a woman, and I love to babble on.
Sometimes being verbally reassured is not enough. If my girlfriend says "honey of course I want you" - but she's not attempting to have sex with me for three weeks, I'm not going to be reassured. So I'd say "you don't seem interested in sex... why is that?" she might say she doesn't want me any more... that she's been wrapped up in a hot new guy ... or she might say that she's actually been feeling like I didn't want sex. My constructive aim for that communication is 1) find out why something is happening 2) find out if we can do something to improve it.
If I just keep saying "you don't seem to want me any more" every day, we're not going to get anywhere.
You have to try to know what you want from a conversation... even if it's just to simply get it off your chest. That works too. Sometimes I'll say to my girlfriend "I don't want or expect you to do anything about this, but I'm just feeling a bit pangy about all this dating you've been doing and I wanted to let you know where my emotions are."
Either way, you're stating a purpose for the communication. This makes the listener feel that they can help. A listener always wants to help. It makes them feel good and stops them feeling like they are just the pit for you to throw all of your bad feelings into, for no purpose.
The same thing goes for your girlfriend... if she says "I need to sleep with people in the future" and you stonewall her... what's that going to do? It's going to make her go inside herself and feel that she can't communicate her needs with you. If you say, "OK, what practical things can we put in place?" this could really help both of you.