delusion?

I'm an older teenager. I'm in a group of friends and I always feel like I'm the last to know about things. They planned a party after our prom and I didn't get asked to go until 10pm the night before even though I KNOW they'd been planning it for weeks as everyone was talking about it. I feel like I only got invited as a last minute thought, and by someone who I see as one of my best friends, though I think its not reciprocated. The worst part is it isn't the first time its happened and it just makes me feel like they don't actually give a shit about me at all!