In relationships I don't really communicate well. I feel like bringing up occurrences where my SO acted inappropriately shows neediness and insecurity. So I adjust to the situation and I act the same way she does. One thing leads to another and I invariably end up in somewhat toxic relationships.

Recently me and my gf (1 week official, 9 months hookup) we went to a party with a bunch of friends and my she danced with another guy. Don't really care per se, but it was a sloppy dancing and they were way too close in my opinion for it to be innocent friendly dancing.

Huge red flag in my book. I almost dumped her on the ride home but I figured I'd do it on a sober mind in the morning. But while drunk me was ready to dump on the spot, sober me is a bit more pragmatic and Machiavellian - no need to break up with her, just fuck her, cheat on her and keep an eye out for other potential girls I may wanna date. Yet this line of thinking gets me in a very unhappy, unfulfilling relationships. I go to a bar with my gf and I'd have to be constantly on the lookout for side-chicks. She goes out with friends and I question what she really is doing. Shit like this kinda adds up and takes way too much of my time.

So at this point I have two options - either I dump her or I confront her. I want to confront her as it will be a learning experience.

And there is my question - how do I go about confronting my girlfriend about inappropriate behavior without sounding needy or insecure?