Relationship problems

Hey everyone, i’m a ftm to my gorgeous boy who I had 6 weeks ago. I’m getting to the point now where I just don’t know what to do in my relationship, me and my partner are young, 22 & 21 and it is just so hard. He broke my trust while I was pregnant when he was dancing with other girls on holiday, messaging other girls etc when I was about 16 weeks along. We were very very early into our relationship and both unsure whether we wanted to keep our baby at the time but obviously decided together afterwards that we wanted to keep him. He said that he was scared and unsure on what he wanted which I do understand and I did stay with him, however i’ve never truly gotten over it and if i’m honest i’ve not ever been 100% with him since. He tries to get the girl that I was out of me and he has apologised so many times but it is hard, sometimes he says that I am always horrible to him even tho I really don’t try to be. It’s been 7 months now and haven’t really had any big issues like that since until a couple of days ago when I found a message on his phone to another girl 12 days after I gave birth basically calling her fit. There was no conversation between them since that. When I called him out on it a huge argument erupted and long story short while arguing he spat at me while I was holding our baby. This all sent me into a downward spiral and since then i’ve been feeling really low, had thoughts about suicide but I know I would never do it because of my baby. Yesterday I had a chat with my partner and said that we need a fresh start where both of us just give 100% to eachother and we need to be kind all the time. However i’ve just been having all these thoughts about how i’m just not happy, I sleep on the sofa every night and have done since about a week after he was born as my partner can’t deal with the noise he makes in the night, he rarely does a nappy change (i’m talking maybe one or two a week) and never does anything like bath time / any feeds unless I ask him / putting baby down for a nap etc. It’s so hard because I love him and I want to be with him but I just feel like I deserve so much better but he doesn’t see that, he thinks he treats me so well. What do I do? I feel like I can’t be happy with him but i’ll be so miserable without him