Lonely confused

I want a serious relationship I'm not very outgoing when it comes to talking to new people in person there is this one girl I've known for about 3 years and I care for her alot she used to want to be with me but she was to young at the time legally and we had a fall out but I just got out of jail and we became friends again and I just can't get her out of my head in a way I'm obsessing over her and i no it wouldn't be a good time to get with her even if we do end up together but I just can't get rid of these feelings