Torn, broken relationship, adultry, with child?

My significant other (Jacob) and I have been together for about 4 years now. We both liked each other in high school and ended up with other people, so once we were together, it was like the stars had aligned. Since that very innocent time, so much has happened, I can't even begin to make sense of it. The beginning of our relationship was exciting, fun, and secure, which i loved. Everything was great, until he started talking to his ex-girlfriend who had broken up with him before me. He had a difficult time, not only giving her up as a once was loved, but closure on the entire relationship. We discussed it, and I knew what was going on and nothing happened with them, but a kiss... This was right before we broke up the first time, Within a week we were back together, him having "chosen" me over her. Life went on a usual and then tragedy struck in his life. His best friend died in a horrific car accident and it changed everything, his outlook, his demeanor, his humor, his depression. He has bipolar disorder and so we deal with that on a regular basis, but it took a toll on him and he was not himself. This was about the time that our relationship took a turn for the worse. We argued constantly, he was always angry but i still loved him. I lost my virginity to him, so of course I was very emotionally attached. But he started going out a lot more and lying... to make a long story short, he ended up having a very long drawn out affair with his ex and a few others along the way (all of them knowing i was with him). I found this out on my 20th birthday by his best friend at the time who actually liked me. So we started talking, but nothing came to fruition because i loved jacob so much. I stupidly stayed with him despite the bitterness and hate that also stayed because of his betrayal. From this point to the next, he asked me to marry him, which i kind of answered yes (not being completely sure about the answer). A little while after this happened, the relationship began to sour. He was jobless (for 9 months) and lived with his dad, and I had to buy everything, and pay for our dates or anything he needed, I had alot of resentment towards him. During this time, I met someone who i was attending cles with at college. He was nice, employed, educated and took my mind off of things, I tried to break up with Jacob. I told him that it wasn't working out, and did so with not much emotion because of how betrayed i felt. Not but a week later, he contacted me and asked to take me out. (come to find out later that he had pawned his electric guitar to take me). Through talking at dinner, i found out that he was actually going to kill himself the next day. he had everything planned and that's one reason he pawned his guitar. Upon finding out this, I couldn't bring myself to just let it go, so we ended up spending more time together which ultimately turned into and relationship again. and this is where the fun began. a month later I found out that i was pregnant. I got kicked out of my mom's house, and we moved in together with his sister. HUGE MISTAKE. We fought non stop. things got violent. so his sister kicked us out. we found another place in the nick of time, six months pregnant, and we both had full time jobs. things were good sometimes. we still fought and things were still violent sometimes, but i was happy mostly, and we were friends. then we had our baby, a beautiful baby girl (emily), and we both adore her. our relationship was still very rocky, sometimes i hated him more than i could stand. he hit me, ignored me, and brought me down. when emily was about 9 months, i met another guy at work (Paul). we texted back and forth, just starting as friends, and eventually lead to something totally different. i was in the hotel room that my work put me in because of flooding and texted paul to join me, the first step i'd made to become ual with another man since jacob, when jacob showed up at the hotel and ended it before it started. I never ended up having with Paul, which im not sure if im happy or regretful, but the issue is, the reasons i strayed never got better. I'm still ignored, abused (hit with objects), and used. But i just can't bring myself to leave him. At the best of times, I feel like he is my soulmate. We have alot of interests alike, but also alot different... But my daughter's life would be greatly affected and i come from a divorced family, so i understand what it's like. And I'm so scared that it would be a mistake to leave. What if I can never find someone like him again? What if i dont find someone who appreciates my quirks? and the thought of leaving him and not having him in my life makes me sick to my stomach and indescribably sad. Plus I'm out of work for school, so i can't even support myself now. And he loves emily so much. It makes me so happy that he is such a good dad. but im still unsatisfied, and unhappy. I'm so torn