Looking for the name of this confusing movie?

Okay, so a few years ago i saw this movie and it was about a guy that kept going back in time. It wasn't back to the future or anything like that. One scene I remember was that an explosion happened with a kid and his arms got blown off but it wasn't gory at all. And I think his girlfriend died and at the end he saw somebody who looked just like her then the movie went off. I really want the name of this movie! If you can help me I'll be very grateful!