How to deal with an unclear situation with my ex-husband

Good evening, the situation is such - lived with a man for 3 years. After I got pregnant, and at six months he had another girl. We separated. His girlfriend hindered communication with the child, he came rarely, but alimony is always paid. At first there was a lot of anger at him, but over time it passed, we just communicated calmly. Now I do not understand what is going on. After 4 years, he came to the child and stayed for a couple of days. All those days they played all day, stopping only for naps and lunch. In the evening when I put the baby to bed and we got to talking, he kissed me, to which I reciprocated (the relationship was after him), but his lips are just so familiar and I couldn't resist. During these days there was no more kissing or anything else. He kept trying to snuggle, hug, kiss. When he left, he also asked me to walk him to the door. I walked him to the door and he kissed me there too. My question is, what was he doing that for? Did he want to come back? I, in turn, have now filled my head and seems to have fallen in love with him all over again. What to do in this situation, how to deal? Now I think about him all the time.