I need advice😕

For like the past two months my boyfriend, of a year and a half, and I have been arguing non stop about the same thing...another girl. I have no physical proof that he may or may not be cheating but it's got my anxiety through the roof. He has been distant and they snapchat ALOT which irritates me because I can't see the messages. He gets pissed off and defensive anytime I bring it up. He says they're just friends and I should trust him. They've had a snap streak of like 20 days going and she's his number one best friend yet she doesn't show up in his conversation feed. I had had enough and messaged her and she played stupid saying "who?" Then immediately messaging my boyfriend asking him what she should tell me because she didn't understand why them talking all the time was a big deal. This set me off. Our sex life has been in the toilet since we have been arguing and I feel like I'm always getting told no. I don't feel like a priority and we haven't gone out just the two of us in like 6months. I'm just stuck because I feel like my judgement about the situation is clouded because we live together and are currently building a place to move into together. I just feel unattractive and down on myself all the time because I always feel like he doesn't care. We have different views on the future, ex: I want kids and he says he never wants kids with me. I mean he does a lot for me but I think he thinks that spending money is showing me he cares when all I want is to spend time with him. I feel like he is pushing me away and I give my all. I'm trying so hard to make it work and it feels pointless. I asked for a break and he didn't even really care. If you spent the time to read this whole thing I really appreciate it, you're awesome. I don't usually vent but I'm at a dead end and don't know what to do.