I am sorry you struggle. You seem pretty sad.
I mean this kindly, ok? It may not be what you want to hear.
Are you
monoamorous (want to love 1 sweetie) and prefer
monogamous relationship shapes that are 1:1, no other people? Not crazy about him having random NSA casual sex, and not crazy about him having another serious GF either?
If so... why are you going against your own grain and participating in (an open/poly shape) thing that is not (1:1 shape) like you prefer?
If he is not into doing Closed/Monogamous? And you are not into doing Open/Poly as a mono endpoint in a "V" or similar? Then you guys might like or love each other a lot... but it is not enough if you are in the wrong relationship shape. That's the road to heartache for one or the other if you guys want different relationship shape models. He would be sad in a Closed thing, you would be sad in an open/poly thing.
Sometimes the most loving thing one can do is set each other free. Then he is free TO open/poly date and you are free FROM all that.
about 4 months in he told me he wanted an open relationship. Which I went along with because I do not want to loose him.
Are you participating in an open/poly thing (even though you don't really want to be doing either) in order to avoid breaking up? If you are doing this... I suggest you stop bending yourself into pretzels. It doesn't sound like doing that behavior is making you happy.
Might have to come to terms with the fact that breaking up is sometimes part of dating. Not everyone you date will be deeply compatible or a long haul runner.
Dating is
how you sort all that out and find the deeply compatible ones.
When you date, you could not compromise your values or sacrifice yourself for the relationship. In a healthy relationship you have to be able to say "I love you. But not even for you will I do stuff that hurts me. " If participating in this is hurting you? You could stop.
I’m at a loss of what to do. I just moved in with him, and I don’t want to move back to my parents basement. I just feel like I cannot compete with her
Could not compete. Could stop participating in things that upset you.
If you don't want to move to your parents' basement, consider moving out to a flat of your own.
Or if you need to move back home as a stepping stone to moving out to a flat of your own -- could do that.
Galagirl