OK well lets get started from the top about 3 years I started going out with this girl and it was just anther girl friend to me I didn't think anything of it at first. Well we got and we ended up falling in love well we were tother for about 2 and half years and we ended up breaking up mainly cz I my trusting problems. So we broke up I hit rock bottom. I started doing things I never thought I would ever do. I started getting to trouble. Well about a year of this went by and I met this other girl but she is only 14 and I'm 17 and the last I was with was 17 also. Well me and the 14 year got together and the same thing kind happened. I we fell in love with kind. Well 3 months went by and I went jail for a month and when I got she was still there but the spark that we had was gone. And now I get a call from the last girl saying that she misses me and she wants me back and I want to taker but I still love the one I'm with now and I'm scared of her hurting me again but I still love her more then any thing in the world but I don't want to hurt the one I'm with now. Can some one help with my problem

You say the spark is gone with the 14 yr old. Is that how you feel or is that how she feels or mutual? Sounds like you need to sit down and have a serious talk with her about everything from what she wants in the relationship, if she sees it going anywhere and work out what you two want or don't want.
Your old girlfriend could possibly seriously had a change of heart and want to make it work with you. If it ever came to the point of possibly ever getting back together you need to not make the same mistakes and you need to talk things out so that you are on the same page to not end up in it failing again.

Your willing to love, and when you love you love hard. Don't lead these girls on, and have them going through the same thing you went through after the break up, fight, or whatever the situation may be. I think you should be honest with your girlfriend, and ask her where's this relationship going?? Her being 14 and you being 17... it might not last too long (my opinion). Can you trust you ex with your heart again?? If you can, and if you're OUT of the relationship with your current girlfriend take things slow and see what happens.