Still having sex with ex

So my ex and I broke up two years ago now due to losing a baby. However we still kept in contact and continued our sexual relationship. Well I’m December we decided to try again when I came back from school however one day he was being so dry over text and what not then explained that we ‘had to talk’ anyway come to find out he got another girl pregnant (she was married to someone else) and I just didn’t want to know anything about him and I was done. However, that changed about a month ago when he snapped me and we started to talk again went over to his place and had a heart to heart and we ended up having sex after crying about losing the baby because we never really talked about it and were kinda forced to forget it even happened. This continued and we talked about how there’s something between us that we can’t stay away from each other even after so long and even after we say this is the last time. One thing that hurts me still is that he is having a baby with someone else but yet we have constant sex. I don’t feel guilty about what I am doing but I am unsure with my feelings and don’t know what to do about it. I could really use some advice.