Replying to Please read..

Me and my gf have been together for like 3 years now almost, and we have had our arguments and whatnot. I feel I have had her pretty much where I wanted the first two years and I could pretty much do the things I wanted within some boundries as go out and hang with my friends alot etc. Lately I have lost abit of the "controll" I had, and I felt like I was loosing her if you know what I mean... And all of a sudden I started getting jealous which I never had been before and wanted to know where she was at all time and such. She began to go out saturday nights more than before and I was not to comfortable with it although she has delt with me doing that from the very start. Anyway, she works with this guy at a restaurant, this little kid a few yaers younger than me (I also happen to know him pretty well). The sendt eachother sms's ocationally, nothing much. She told me it was nothing. Weeks past and my gf went out of town for a Gwen Stefani concert, and when she had returned I was at her place and she was in the shower and all of a sudden her phone rings, and its this little piece of crap she works with, who wants to know if she came safetly home from the airport cuz it had been snowing and she had summertires on the car. which just toped the whole thing. So first saturday night out I track him down and give him a real pounding telling him to stay the fuck away. Next day my gf freaks out telling me their work relationship is now ruined and she is embarassed to even say hello and such to him. They had been working together for like half a year and known eachother since comprehensive shcool. I kinda know there was nothing going on but I was so pissed off with the way he just tried to approach her.
So what would you guys have done in such a situation? Was what I did wrong?
Id like to hear some girls opinions on her freaking out because of this guy taking a beating from your bf. I dont think there is any reason to freak out because of it.
Fuck!