Taking trips without the SO

Kelsey • 23-in love with my wonderful boyfriend- beautiful step daughter, pregnant with number 1 😍
Okay so my cousin planned a trip to Florida a few months ago and everyone that planned on going with her backed out. My cousin and I are both 23 and very close. She asked me to come with her. I told my SO that she asked me and asked his opinion on me going and he's basically saying I can't go. I don't drink at all, but she does. And he said "why would I want you to go 1000 miles away to hang out with someone partying for three days?" It just seems like he doesn't trust me to go and I'm really upset about it because I would love to go and just get away for a few days.