I was with my ex 3 1/2 yrs she was 2 weeks pregnant when we met so I consider her daughter mine she had been hanging out with a new girl friend of hers and went out no big deal except she didn't call or text to let me know she wasn't coming home I told her it was over but thought we would get through it just like another fight but I had to leave town for four days when I came back she said its over for good and has moved out she says she still feels the same about me but isn't willing to let me hurt her again her friend had been saying she needs to do better than me and had been introducing her to guys at the bar she swears she hasn't messed with anyone but told me she wasn't doing anything on a fri and sat night only for me to find out she was at the bar I still am in love with her I feel it whenever I see her smile or we kiss or our hands touch I don't know what to do

You told her it was over for a petty reason, not telling you she was out with her friend. You 'thought' that wouldn't mean what it means, then you took off for 4 days. Why would you be surprised that she moved out?
Now you lost her. Learn from this for the next person you meet: mean what you say and say what you mean.
If you want to try to apologize to her, tell her that is what you have learned and won't do it again.