what do I do

A little over 6 months ago my ex and I started talking again after 11 years of being apart. We have a 14 year old son together. She is now living with me and my now 3 year old son. problem is when we started talking again she was with a guy. she started sexting me and rehashing old feelings. I never stopped loving her since it was me that messed up the first relationship. Any way we have been back together 2 weeks. she moved here for me to get away from him and his abuse. I have recently found out that she was not only sexting me but at least 7 different guys. she has been talking to her ex telling him she misses him and wishes that she never left. But than turns around and tells me that she loves me what should I do. Silly thing is my 3 year old has grown attached to her in the 6 or so months. what should I do tell her to kick rocks or ask her flat out what is going on hoping she tells me the truth. and if she's lieing what than. Any advice would be great.