Am I overthinking about my ex?

Ok I have to ask someone who better than thousands to millions on the Web? Assuming this is an appropriate place to put this, if not a subreddit suggestion is welcome.

• Ok so recently my soon-to-be ex-wife/mother of my child began talking to another guy, we've had our problems and I was okay with it at first because we plan on divorcing ASAP. But after awhile her sister came about doing her thing with her own set of dude(s) and in the words my wife they both trying ”ho” I guess while I'm trying to focus on me. I was my wife's first and only for the last 5 years and she was the only real relationship I've had. Once again I was cool with it, not really trying to give a fuck cause I'm damn near out the door. I'm pretty nonchalant person when it come to most things.

• But recently I've been overhearing the conversations (not even deliberately listening, they're just loud), not something I actually want to hear; wife basically want to fuck ol’ boy and her sister is encouraging her. And last night was the night I guess. They left (circa. 7:30 pm) and I myself not being stupid say have fun (I'm still in the house for time being), to which she just has this excitable expression on her face and that made me feel some type of way (anger maybe?). I put my kid to bed at 8 pm, then cleanwe up, watched TV thinking they'd be back by 1 or 2 am.

• Her sister returns at about 4 am with the only car we got. Mind you, the house we live in is 35 miles from anywhere and apparently the guy lives 30 miles plus the 35 so a total of about 65 miles away. And her sister left her because she said ”kick rocks”. No ride and alone with a guy she barely knows. Side note: They both have a history or being taken advantage of. So I've no clue what to think. As I'm writing this it's 5:30 am. I'm at a loss. It's not that I want her back, that's BIG negatory. But I honestly don't know what I feel. I'm tempted to drive the hour and change to make sure she's okay. Literally to make sure she's good. I understand she's an adult. But she is the mother of my child and her sister left her. Alone. Am I being dramatic, because I've never really felt this way. The worry is nauseating and I can't sleep.

• Also does me ”allowing” (for lack of a better term) her to fuck another dude make me a cuck?