My pregnant girlfriend left me for no reason?

My girlfriend left me about a week ago now shes 3 month pregnant and has yet given me a good reason why she wants a break. We talked and she ures me it was nothing i did and that in fact i was as she put it "prince charming" she said that she simply woke up one day 2 weeks ago and didnt like me even though thats the same time she said all she can think about is how lucky its ours and she cant wait to spend the rest of her life with me. Now she barley wants anything to do with me she said shes fine seeing me once a week but does want me there for the dr appt and during the delivery. I have taking a backseat to her and all she seems she wants to do is hang around and be with her ex boyfriend who she says there just friends but i believe its more then that but part of me believes her cause they have been friends since like 1 st grade. but its the fact they still dated and after she broke up with me she starts hanging out with him again but really could careless if she sees me. she did say when we first broke up she needed space and a time to find herself which i understand but now im starting to think its something else cause now shes saying she wants to just go out and date and discover new possibiltes is the way her and her friend put it. there was nothing wrong with our realtionship and we never faught we bickered but thats about it so if someone can pleas help me id appreciate it. i want to be in that babys life and be there for her whial she goes through this and not be just there for the dr apts and some guy as it seems now she wants to see only once a week. whial haning out with her ex everyday.