"a little obsessive" - to be honest I'm only saying this to help you, it is more than a little obsessive. 5 months after a break up you should be moving on. If he hasn't given you "closure" however you're expecting it, you're not going to get it. The fact that he's blocked you multiple times on fb says to me that you're looking for him to fix your problem and not thinking at all about him and the space you should be giving him. Continually trying to contact an ex that has clearly moved on is not doing anything for you or for him at all. For you, it's only continuing to exacerbate the wounds that were inflicted initially. He left you and you feel rejected. To continue and try to get him to respond to you in any way is just setting yourself up for continued and repeated rejection which in the end is going to leave you wounded more and bleeding on the side of the road.

I don't have advice as to what you can do to make up for the behavior. I wouldn't worry about that at all. Move on, and take care of YOU. If you don't have a therapist, please, get one, you need someone to get your head straight about this situation and get back on your feet. The relationship is gone and over.

Again I dont' say this to be cruel, but to be honest. You have to come to terms with what you're dealing with or you'll forever be stuck in hurt, victimized mode.