Missing Him

So..... i was dating someone for 2.5 years, and this was over 10 yrs ago. I broke up with him because he had started getting into drugs & I didn’t see myself with him for the long run because of this issue. Clearly after the breakup I was sad but got over it pretty fast. Fast forward 10-11 years, and I’m now married with 3 kids to my husband (not my ex).

The weirdest thing is that for the last two months I can’t stop thinking of my ex. He just pops in my head randomly and I can’t turn my mind off. I just constantly think about him. What the heck is going on? How can I stop this?!?