I read your post and it really touched me. You seem very mature and responsable, your daughter is very lucky to have you has a mother
I know exactly what you are going through because I've been there. I had my first daughter at 17 and my second daughter at 19 years old. They are 19 months apart. Like you, my friends kind of disapeared, anyways I wasn't in the same reality as them anymore... It's a hard journey that you're beginning but one that is all worth it!
Going back to school is a very good decision. That will make your future a lot easier. I know that you feel lonely right now but take advantage of the situation to get closer to your family. I grown closer to a couple of cousins of mine and we are still very close. When you will start school, you will meet new people, more mature and maybe in the same situation as you. They will become your friends that you will be able to relate to. So hang in there! In the mean time, go visit aunts and cousins ;-)
For your ex (father of your baby), I can not give you advice because it has to be your decision. You wrote that you are unhappy with him, that he makes you unhappy and that you don't have much interest in common. It's a big decision to make but you already have made it. You broke up with him right? Also you mentionned that he has problems with justice... What I think is that what is the most important for your baby is to have happy and balanced parents. It sounds like our ex boyfriend is still very imature and maybe not ready to be a father right now. He needs a little time to get his act together and maybe he will change when he realises that he's missing out on getting to know his daughter and seing her grow up... In the mean time, you have to think of you and your baby! Also, you're very lucky to have your mother with you, I hope you let her know that you're greatful.
I think you will do just fine! If you have any questions for me, feel free to ask! I did a pretty good job myself! Has for now, I'm 36 years old. My daughters are 17 and almost 19. They have both gratuated from ice school and they are both in college now. It's still not always easy with them but we have a wonderful relationship, we are very close. They are the biggest love of my life and it's beautiful to see them grow into women. When they were toddlers, I used to see this day has so far away! But I tell you, time flies by so fast, the next thing you'll know is that she will be all grown up and you will get your freedom back
Oh, and another advice; don't rush into another relationship. Take your time to get to know the person before making a move because you have to make sure that he's going to treat you and your daughter right. You are her only protection so be cautious and continue to make wise decisions.
Hang in there, you're not alone!