Married people, at what point does this possibly turn into?

I do the same. I am marryed and i love my husband but i do think about my first love and i know how he is doing cause his sister tells me everything. and i do wonder sometimes what would happen if we just ran into each other what would i say what would he say what would he do what will i do. and my favorite song that reminds me all this is a song called, what could have been. Everytime i hear that song he pops in my mind. also i have ran into my first love at a wedding shop with his now wife and when i seen him i hid from him and he seen me cause his sister called and said my brother seen you even though you try to hide from him. yeah i didnt think that would happen. but any ways i know how it feels. i sit and wonder what he's doin and if he's happy. and i'll be seeing him next month cause my friend(his sister)son's birthday and she wants me to come and i know he'll be there with his little girl and i have no clue what i'm going to do. any ways.....i dont think it's wrong to think about how someone is doing and wondering if they think about you.