I can't quiet my head

Very long story but I will keep to the main points. A year ago my partner whom I lived with in a lovely house with my two children up and left me the same day I started my new job. We lost the house and me and my two children had to move back in with my parents. My children are 9 and 5 and I am 26, your math is correct, not necessary for my problem but just to give an idea of my life. I wasn't devastated when he left me and didn't eat for three months, did my best to be a mum and to do my new job. About two months after he had left I got a message from my boss from my old work who asked me out for a drink, the choice was to go or to sit in the middle of all my things that my dads dog had urinated on so I went. He was really lovely but unsurprisingly my head wasn't in it. We went out a few more times and I stayed over at his house on two occasions, my children was staying at their dads house (a different man altogether we had broken up when my youngest was a baby because he wasn't very nice to me and it started to border on abuse.) My ex boyfriend then got into contact, the girl he had left me for had turned out to be using him and he was in a dreadful way and he needed my friendship to help him through. I went because I always think being kind is better than anything else but unfortunately this meeting made m realise that I don't like him anymore, in fact I found him a little creepy. I realised I did maybe prefer my old boss' company. Now he wasn't from around here and he didn't have any friends or family, not sure why he moved here in the first place, and he was home sick, his home being three hours drive away. He left and ghosted me. Which I didn't notice for a while because even though I preferred his company to my ex's I still wasn't infatuated. Over Christmas my youngest got chicken pox and I was trapped on the sofa without much to do as she slept on me and I was tired from being up all night with her so I'm afraid I did persist a little with my old boss as to why he was ignoring me. He messaged me back apologising and saying he missed home. Accepted that and it wwas fine. I then went to my old work to see a friend and he was there but he blanked me. I messaged him a friendly message that evening and he again apologised. A month later his facebook is all about how in love he is with his girlfriend, he was most definitely single the times we went out together I'm not accusing him of foul play or anything. I'm happy for him and she seems really nice and I know he was miserable down here and I liked spending time with him but I have little spare time what with two children, work and I'm doing studies so I can get a better job. My brain however likes to have a wander and think about the very few times we spent together and even I'm ashamed to say, how he's probably not happy where he is now, which I sincerely hope is not true. I can't get my brain to stop and it has embarrassingly been 8 months since I last spoke to him. I don't have feelings for him I'm sure I think I just see him as a 'saviour' from hurt over my ex leaving but now I'm getting a fake hurt over my old boss and I don't think it's healthy. Also I don't want to think about him anymore it's annoying. Can anyone help me with inner peace and happiness for being single?