I have the same problem. I don't know why it is, but whenever I'm left out of anything, for any reason, I feel extremely upset, personally hurt, and begin to have suspicions that they don't like me anymore and make fun of me behind my back.

For example, I learned after the fact that my cousins had a party. I never got a call and had no idea it was going on. To say I was upset was an understatement. I was ready to cut all of them out of my life. Turns out they had invited me on fb, but I had no computer access at the time, so I never got the invite...