In love with my Ex, she left me but she can't commit to anyone else cause she isn't over me.. what do i do?

Okay, I am still in love with my ex girlfriend. She broke up with me and keeps telling me she's finding it hard to commit to her new boyfriend because she's not over me. I know I should get over her but I really don't want to because she's the only person I've ever really been happy with. I still want to be with her and Its impossible for me to move on whilst I'm still in love because I wouldn't be able to actually enjoy another relationship if I tried. She keeps giving me signs that she still at least likes me but then the next time I see her she could have changed her mind and just forget about it or for example until today we still hugged a lot and when we met up we kissed on the cheek then today she decides that's not the proper thing to do when she's in a relationship and she should stop. I think she might just be playing with my heart strings because I personally don't see how, just as an example, a kiss on the cheek is improper. Can anyone make any suggestions on what i should do or weather in your opinion she's playing with me. Be both brutal and honest because it will help me see. Thank you in advance :)