Fantasising about ex?

I’m in a 7 year relationship with 2 kids. In the whole time me and my partner have been together I’ve never spoken with this ex (we were never actually together, just slept together the odd time). This ex messaged me last week asking how I was and when I asked why he messaged he said he messaged me as he was wondering how I was doing (our mams are best friends but I rarely see him). Ever since he messaged asking about our family which I feel was innocent, I keep thinking about times we were together and fantasising about sex with him (it was amazing at the time) and I have no idea why, I’ve never thought about him before this, I’d never cheat or anything like that. I don’t know where this has came from. I don’t know if it’s normal to some extent as I feel like as much as I love my life and family right now it’s very much the same everyday and it’s literally just a fantasy? Not sure if it’s normal in any way at all given my relationship is not exactly exciting with 2 toddlers and we’ve been together a long time

Fantasising about ex?
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