Can somebody smack some sense into me PLEASE?

My ex added this girl on facebook, shes from another town and maybe hes seeing her, or interested in her or something, I don't know how he knows her. I know its none of my business, I know im being a freak. To make it worse wev been broken up well over a year and im being a psycho trying to stalk this girls page but everythings private and her profile picture is of a cartoon so I cant even see if shes hot. I really thought I was over all this. I mean the guy treated me like a piece of crap on his shoe for 4 years and his friends did the same. I haven't found anybody else, like guys have been interested in me but I haven't found anyone im even attracted to or interested in at all. Why am I bothered by this? I think maybe its the thought of him moving on before me since hes the one who tried so hard to get with me and treated me like crap then broke up with me after 4 years. Ugh.