A genuine question

Ok so I don't really have any where else to ask this so...I would appreciate someone's uninformed opinion on me...I have a lot of trouble finding and keeping relationships because I don't really understand social things...my last boyfriend dumped me on my birthday because he "found a girl he wanted to be with, so if it's okay we can just be friends." Which at that moment he was the first person I had ever felt what I thought love was supposed to feel like (warm comforting and fuzzy) I cried for months because I couldn't understand why he would do that to me since we had been together for 5 years...I do struggle with severe depression (which he knows about) and it came out of nowhere...so my question is was it something I did wrong? I couldn't ask him why because he blocked me and wouldn't talk to me...sorry for the random question about this...