Relationship problems (Long)

Okay so I just need to vent . At first me and my boyfriend/ ex fiancé were extremely happy in the beginning of our relationship before I found out I was pregnant. While I was pregnant he was working his regular shifts plus over time shift as a senior Paramedic was never really home and I had to beg him just to come to some of my appointment with me . It was so bad my nurses and doctors thought I was a single mom. He only really came to maybe 3 appointments with me mind you this is my first baby and he has two daughters with his previous wife. 
We got into tons of arguments because I was extremely lonely and could never spend time with him he was making more than enough money working his normal shifts but instead he kept taking overtime shifts so he would've gone from 7am -7am the next day , 7am - 7am two days later or even comes home at 7am and go back to work later that night so I was extremely frustrated always being by myself. 
After I had our son he took a month off and he was absolutely fabulous he helped me with the baby and we even alternated when we would get him like he would take care of him during the day so I could nap for a few hours and I would be on night time duty. 
Once he went back to work he stopped helped all together and we both worked . We only have one car so arguments would happen because he would need to car for work and I would have to work as well it got so bad I cut my hours down to only three days out of the week and even then o had issues getting to and from work because Uber and lift were way too expensive for me to pay for everyday. 
He stopped working for the ambulance company and now works part time as a firefighter and does Uber everyday even the days he just gets off from work . So we never spend time together and he doesn't help with the baby what so ever. We are constantly arguing because I get so worn down dealing with the baby all of the time and get absolutely no break on top of having to work so I would have to deal with the baby everyday during night time and day time even though I have to get up for work . Sometimes he would be off the next day and still would not attempt to help me with the baby at night or during the day . 
So on top of him not spending time with me and not helping with our four month old son . He's constantly yelling at me about how expensive the bills are and how stressed he is about paying it and it infuriates me because he always screaming how it's my fault but most of his bills are from his ex wife and she is basically living for free because he pays her rent which is about $900 as child support because that was part of the divorce but he also pays for her car note and car insurance ( he even has her on his insurance still) which he doesn't need to pay for he says he's doing it to be nice and so his kids have a way around . What makes me mad is he's paying her bills plus our bills so he's paying double everything (both rent,car insurance , car notes) along with me and his phone bills , water and other things . So the expenses are mainly between him and her . I have been going months without a vehicle     But he made sure to buy he a vehicle as soon as possible because he said it was for his kids but I have our son and he still hasn't got me a car despite how hard he sees it is for me to get around I have to cancel most of my son and I appointments . 
Also he tells his mom all of our business doesn't matter if it's big fights or small fights so his mom hates me and told him he doesn't need to be with me which is extremely unfair because he never tells what he does wrong just always me. Idk what to do its soooo much going on so now we are separated for a few months we love each other but he is a workaholic cannot balance family and his job , too much baggage between his ex wife and his family doesn't like me now because of how much he bashes me