Is my view of this wrong?

Ok I'm a 17 year old gay guy, it's my personal belief that when I'm dating someone or they are dating me, there's no need for me or them to go hang out with other people, or makes me feel like I guess insecure and I wonder 'why does he need to see them if he's with me? Am i not good enough?' and i get pissed. Also, I really get upset if someone says something like I need space, my thinking is if you need space be single. My best friend says I'm wrong, and I want other people's opinions so Is my thinking flawed?