Wha am I a mulehead?

Why is it that I try to do things right, but then in the end I freaking fail? Why? I saw my girlfriends mom and I decided to help by keeping her mom busy, so she can leave without being notice, but as I did she told me straight up "This is the time I hate you the most!" You know how bad that hurts? I try to do the right thing yet I do it the wrong way.  I just get so emotional at times like this. Afraid she's going to split with me. Afraid she is going to say its over. She doesnt deserve an ass like me. But she keeps me. I know deep down she loves me, but if I keep doing things like this one day she will leave me. I just can't see my life without her. If anyone knows how to help please help me cause I just wanna overdose and die, smoke myself to death something like that. I need help, because I hate being like this, trying to protect her but hurting her in the same notion. Sincerely,Kyle M. COlin    AKACuddly Panda