Stress, scared and confused and oh yea pregnant

Hello fellow mommies 🤰🏼🤱🏼 so I need some advice. This pregnancy has not been the easiest. I’ve had two miscarriages before I got pregnant with my son leeylnd he’s my rainbow 🌈 baby and he’s due in March!! So this is all completely new to me. I’m scared I’m terrified I don’t know what I’m doing I’m constantly stressing over if he’s growing okay becuz the doctors put me at a high risk pregnancy and I’m also only 114 pounds I started out at 109 so I haven’t really gained anything like I feel like I should. I do have a eating disorder and I do have depression. And I feel like that already makes me a bad mom 😭. My boyfriend and I got together in June. And be him I did sleep with someone else and when we found out I was pregnant my BF just says that leelynd isn’t his. He has other kids too but they are with their mom. He wanted me to tell the other guy that I was pregnant so he knew that the baby might be his or my bfs. And for the longest time I didn’t want to becuz I took many many many test after I realized I might be and they all came back negative. Well the first time my fb and I had sex he didn’t pull out. So I know I’m pregnant with his baby becuz we found a month after being together. But he swears up and down that my son isn’t his and now at 29 weeks my baby is low weight I’m over stressed and depressed and fighting with him becuz he’s done this before and I haven’t and I’m scared and idk how do this or if I’m even doing this right. And last night I told the other guy that my son might be his and then my bf got pissed we started fight all over again. And he left. And then after hours of being gone he came back. Told me he didn’t want this relationship. And then this morning he’s mad I told the other guy becuz now he doesn’t feel like he’s anything to the baby. He’s mad becuz he’s been here for all the appointments and everything. So now he doesn’t want anything to do with prelude and idk how to deal with all the stress and drama I feel like it’s making me a bad mom and a bad girlfriend I think so low of myself and I hate it I just don’t understand and I don’t know what to do