I feel stupid for still caring

Me and my daughters father were together for 5 years. It’s been 5 months since we’ve been broken up and he’s moved out. As soon as he moved out he slept with someone else that he still lies about & I haven’t slept with anyone.. today on the phone I asked him if he wanted to hang out & he said “no, I’m not into you anymore” & idk why but I felt it in my heart when he said that I instantly started to cry I feel STUPID!!!! For still caring I feel DUMB for not moving on and having sex with someone else.. I feel like he thinks I can’t move on when really I just don’t want to! I don’t have the energy to be with someone else right now.. idk I just feel so freaking sad and pathetic I feel so stupid I even try to be cool and hang out. I don’t want to be with him but that being his response really hurt my feelings