Time for a boundary talk I think.
I would suggest getting a list together of what is acceptable to you and what isn't.
Here is what would be acceptable to me.
-she is your girlfriend, you are responsible for taking care of anything that is to do with her.... ie. cleaning, cooking, planning, washing. I will do what needs t be done for my regular fair share of duties for our family, you get to do what your fair share is and take care of anything to do with her.
-if I can hear your fucking, it's too close, take it elsewhere or be more quiet. i'm glad you are having a good time, but I don't want to know.
-regular quality date time and connection.... me and my partner will sit down and plan a weekly date that is thought out to involve conversation above household talk and some intimate time to cuddle and/or have sex.
-monthly you can go to her house. monthly she can come to us, provided the above is covered.
In my relationships I don't get away with ANY of what your partner does! Frankly I'm aghast. I find it rude and disrespectful, NRE or not. That might not entirely be his fault if you haven't been communicating, so I suggest getting on that so he and she knows what is up for you, otherwise resentment builds and he will be forced into drastic measure if because he has an irate partner who wants his girlfriend gone, rather than your feeling compersion for them. He needs to invest in that I think.
It sounds like you like this woman and don't object to their relationship or her at this point, so I am thinking nipping this in the bud now would mean that you can be sane about it. That is a good thing... no one likes an irate metamour that hasn't been getting their needs met because she hasn't been talking about them.
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