Narsist..what is it like to be in a relationship with them, and to get broken up by one?

my exb/f & i were together for almost 2 years&he began going on antidepressants.. he was previously diagnosed w. adhd & OCD..about 3 weeks after beginning 2 take the medication for his depression i noticed that not just his mood, but his entire personality changed..4 the worse..he became wild & promiscuous & distant, & would try 2 talk 2 every single person in a crowded room...he acted as if everyone loved him and that all the girls wanted him and the guys wanted to be him...his ego just exploaded, then he broke up with me (then asked me back out and broke up with me again all within that week) until finally it was over 4 good (in a matter of 5 days)the weird thing is, is that after the breakup he would alienate me&act like his life was soo great without me..i heard he's been getting involved w/ some drugs but besides that point many people believe that he is either bipolar or a narsist, & i was wondering if someone could explain in more detail what they feel may be going on w. him