She's just starting talking with her ex?

Yeah, so my girlfriend of 1 year and 3 months now as I haven now just discovered; has contacted her ex. She didn't make the initial contact, but still none the less she responded. I know it's probably nothing, as she hasn't replied to him; still even so it bothers me. This man cheated on her, and it had really hurt her. I know she had a tendency in past relations to be drawn back to her exs' and that is why I am worried. I think it was about the same time last month that we were listening to a song on the radio together, and she had stopped it about halfway through. She was saying that it reminded her of her ex. She hasn't talked to me about any of this (Yeah, I'm a horrible person...) thought I'm sure it's in reference of said ex. Is this something that I should worry about? Trust has always been a wavering issue with me in this relationship. Perhaps because it is my first, or perhaps maybe because I have reason to be suspicious. After the second month of us dating, she had told another person that she loved them; and later proceeded to tell me that she was in fact 100% serious (Serious love). And about after the 6th month of dating, she invited over this guy friend of hers so that I could "meet" him. Despite knowing the fact that I am a bit socially awkward, she had proceeded to do so. Though I held through, I could not help notice that the majority of her time was spent catering to him. She was staying close to him, quite intimate in her body language. It was as if they were the ones that were dating. She later admitted to having loved that man as well, though thankfully he did not feel the same; as I might have ended up watching a rather illegal version of pay per view. In all seriousness, that is how serious she seemed about him. Not that I really wish to justify my actions, but this has just really screwed me up. I honestly cannot say that there is a day that goes by that I don't think about these things and just wonder if I shouldn't just leave. I'd like to say I love her. I honestly enjoy being around her quite a lot, but when she is being so immature as to totally and utterly ignore the pain that she is putting me through, and continuously making me question her love for me... I just don't know if it's worth it. I do what I can for her and her family. I do their oil changes, I service their vehicles, I mow their grass, I help out with the dishes occasionally, I've cooked for them, I've helped them move furniture to their sisters home, as well as transport fitness equipment from the store into their basement... I've done quite a bit for her family. Though, it could be said that I could do a little bit more for her. That being said though, I haven't gotten a job yet, as well as I've just been kicked out of school; so it's not like I can just stroll over there with some nice flowers and sweets. I do what I can, and I would think that it would be enough... I can only voice my own opinion though, so that is why I am here to ask for yours. What do you think I should do?