Need advice..open relationship question

So I’m in an open-style relationship with the absolute love of my life, only because we are long distance.

Neither of us go looking for sexual partners but sometimes stuff comes up. I’d prefer if we were together in person, but we both gotta do what we gotta do.

So we have an agreement, we can satiate our needs with whoever we want, just don’t give each other the details.

So. I love my boyfriend. I’m gonna marry his ass some day.

An ex recently popped back into my life after a few years. We had never had sex, but I’ll be in town for thanksgiving break and we might meet up. We’ve recently talked about hooking up, and he knows about my relationship. He’s also recently divorced.

There’s no emotional connection there anymore, just some sexual tension from high school.

So my question is this:

Is it weird to hook up with an ex? Would that be crossing the line?

I don’t like to have sex with people I don’t know, or can’t trust. Not really a one night stand with a stranger kind of girl. The only people I’ve hooked up with are bfs or friends.