Need help! Am i right for being upset????

My girlfriend of 2 and a half years is constantly making new guy friends ever since she got to university. This is understandable and didnt bother me at first, until one guy she was hanging out with WAYYY to much for my liking (almost 4 times a week) she ended up spending the night at his house, she continues to see him on occasion despite my protest telling me they are "just friends" with no feelings for eachother. This is the only incident of that nature that has ever happened. But she is constantly making new guy friends and i feel she is acting innapropriate with them and sending them the wrong message, im not sure if its intentional or not. There have been times where she has been lying in bed with me and recieved a phone call and a guy is asking her to go on a trip to see a band half way across the country, this to me is f*cking b*ull sh*it, pardon my french. Do i have to right to be uncomfortable with all these new "friends" shes making? The other day she decided to call one of her EX-boyfriends out of the blue to "catch up", this pissed me off enough to tell her i needed a brake from her. I am constantly trying to explain to her that I am uncomfortable with her hanging out with so many guys all the time (1 on 1) with her track record, she always turns it around on me telling me im controlling, do i have the right to be upset?