Friends leaving me out

I’m in college and on summer break. I have a part time job for the summer, and I got really close with my coworkers. I have a group of friends that I’ve known since middle school that live in the same town as me, and we’ve always been close. Recently , they’ve been hanging out without me, and it seems like they’re starting to distance themselves from me. I didn’t do anything wrong. I always try to ask them to hangout but they always say they’re busy, and then they hangout together. I feel like they’re upset that I’ve made new friends with my coworkers. I haven’t seen my middle school friends for 3 weeks. I don’t know what I did wrong.