Ex pregnant girlfriend moving on.?

So I left her 4 weeks ago and she moved out. She's 20 weeks pregnant and she's decided to talk to other men (I don't think she will have sex. I just think she likes the attention) I just can't get over it though, I still have feelings for her. I just think she's being a dirty whore. She begged me every day for the past month to re consider our relationship and I kept saying no but now I feel like I want her. I don't know what to do?