4 months NC but...

Not been on here for a while. It's been 4 months NC, no hoovering, and even when his ex (from before me) got in touch and I discovered he had a kid and knew about him the whole time he was with me, it didn't send me spinning, calling over and over. It merely confirmed what I already knew about his nastiness. There's no way I want him back, I'm happier now than I ever was. I am actually grateful that ow was low enough to cheat on her husband and then 'fight' for my Xn's love, rather her than me but.... Lately he's been creeping into my mind.
I know that all the 'good' memories are not real and it really is a small part of me that is bothered by them but last night I even dreamt about him which I've not done in a long time! I dreamt he asked me out on a date and I said yes (eh, only in his dreams! Lol!) but as I was getting ready he was outside watching me. I was suddenly living in a studio style house surrounded by windows and everywhere I went he was at the window. I guess that sums up how controlling and stifling he was in our relationship but my question is is this normal to go backwards so to speak, as in think of them more all of a sudden?!