This sounds unhealthy for you to be in. I'm sorry you hurt.
I can see where you grieve for what used to be between you, but that's not what you have now. And what you have now isn't serving you. So you could speak up.
You could tell her you feel taken for granted when you do ____ and she does _____. You could ask her if she's willing to stop doing ____ or start doing ___ so you can not feel taken granted.
You could ask her if she's willing to....
- meet your needs for emotional connection, affection, etc.
- to demonstrate loving/kind behavior toward you by doing _____.
- go out of her way to do something nice for you
- to plan a surprise for you
- to ask how you are and about your well being without you having to prompt her
- be supportive with a hug, kind words, etc if she finds you feel low
- have sex with you in exciting ways again
If you HAVE asked her all these things before and she is NOT willing/able to meet your needs?
You could ACCEPT that she is not willing/able to meet your needs. Just not gonna.
Then you can choose.
1) Let go of some of your wants/needs and stay in this relationship that is uncomfortable indefinitely.
2) Let go of this relationship that does not serve you. Be sad and uncomfortable for a time and them move toward healing and dating anew at some later point.
Both of those stink. Which stinks less?
I know she's been your first everything. And she seems destined to also be your first break up. It's hard, and it sucks.
But you could be in a relationship where you can blossom and THRIVE, rather than cling to a relationship where you barely SURVIVE.
It's up to you. Choose self-respecting behavior -- stop having group sex you really don't want to have, stop doing favors and chores for someone who takes you for granted, stop sharing a GF that you really don't want to share. You cannot ask her to break up with him. But you can ask YOURSELF to step away from behavior you are doing that is causing you pain.