'Its meaningless'(vent,advice,help)

Tina • Csection on the 29th of Jan :) Can`t wait to meet my daughter
My boyfriend just told me our sex is meaningless and we shouldnt anymore...He said I do it because I want to him just to finish and then move on.Which is technically true because I am 27+3 so my sex drive has dropped....But also I dont know....I just dont feel like doing it....I think it all fell out of place when he spoke to his ex girlfriend when I went away to visit my parents and she tried to mess up our relationship by telling him that I had asked her if they had spoken because idk...I just had a feeling...and I knew he wouldnt be honest so I asked her straight up...and I just got told all of this stuff like he just wants her back in his life as a friend and whatever....And I said our relationship is gone...because it felt like it and she told him....and he nearly ended it...But didnt but I havent felt like I can trust him yet.....I know he still looks at her pictures and he often mocks me about her like lets call our little girl *says her name*...and it sucks.....and I don't know how much this has to do with our sex but Im not sure..sometimes I feel like I should just let him go as much as I love him and let him be with her because its like he would be a lot happier with her.....we've been together for 1and a month...they didnt date...he wanted her so they spoke for a while...he tried for 9months o date her and she just kind of flirted with him/phone sex etc but she also did that with other guys...But her and I were friends and then I started dating him and we just stopped being friends....i love my boyfriend...i just want to fix our relationship......please give me advice...have you ever been in this situation....