What's wrong with my girlfriend?

sounds to me like something major happened in her life to make her want to commit suicide and cut herself and you teasing her and poking her bugged her. I know this part from experience that some people annoy me when they poke me but others its funny. Some people have teased or poked way to often and it gets annoying so just back off on that for a little while. As to the shes been talking to her ex maybe she is liking having something from her past like before what ever made her wanna commit suicide back in her life. Just let her know your there for her if and only if she even needs you, don't try and force her to let you in because that will just make her even more distant from you. If you do lose her don't beat your self up about it, sounds like there's a lot going on in her life that you don't know about. its probably best to just give her her space and let her know that your there for her, good luck