Relationship falling apart

I feel I am at a loss for words with my boyfriend and I need some insight into how ADHD may be affecting my relationship. 

Almost a year ago I began dating my boyfriend exclusively. We had been friends for a couple of years prior and I would question his promptness to events and even questioned if I felt I would be able to be in a relationship with someone who is always late. He was so sweet and genuine and I believed he adored me so dealing with his chronic lateness seemed worth it to me. 

After doing research I believe that when we started dating he was hyper focusing on me and our relationship. It was GREAT! He was so attentive to me and constantly wanted to be around me. That only lasted for about a month and a half until we started having problems. 

He often times does things to people that are disrespectful yet I can tell those are not his intentions. He just doesn't seem to understand how some of his actions are rude. 

We are now about 11 months into our relationship and I am at my wits end. I care about him so much but he tells me every few days when a SIMPLE issue comes up how he feels he is "forcing" himself to be in a relationship with me. Yet, we will spend time together over the weekend and everything seems perfect between us. But when he is angry he says things that seem out of character to me. He gets EXTREMELY angry when he is trying to focus on something for work and I am "in the way". He says now he just wants to be alone and he's "exhausted" with all our fighting. He will never admit to doing anything wrong and most recently he pushed a business partner and mutual friend so far with his unreliability that she does not want anything to do with him anymore. To him this is everyone else's fault but his own and he refuses to seek help when he was the first person to mention to me that he thought he had ADD. 

I'm wondering if this type of behavior is normal for a person dealing with untreated ADD. He constantly tells me that I'm the problem because I "cannot accept that he doesn't want to be with me", yet we are still technically together and when things are fine between us there does not seem to be reason to break up.