I think I'm done

My boyfriend has untreated ADD/ADHD and his coping mechanism for disappointing me is avoiding me/being rude. He started a new job where he has to work overtime every day, and he has been rude and condescending when I try to plan anything. We had an appointment to have our cat's stitches out on Saturday morning, which he agreed to go to. Our cat is hard to handle and I don't have a car, so I needed help. He tends to have "no control" over when he falls asleep at night; he had agreed to come over Friday night. By 7:30pm he still hadn't left the office but said he was leaving soon. I didn't hear from him after that, and then I didn't hear from him all weekend. He lives at home with his parents. I asked him not to stop at home first (which is further from his job than my place anyway), but apparently that's what he did without communicating with me. He had said earlier in the day that his mom was coming home and his stuff was "a mess" at the house. He probably went about his business and went to the bachelor party that he had been invited to on Saturday. This morning I texted him and asked if there was any particular reason why he wasn't talking to me. His response: 'I've been busy." I said so have I; you didn't tell me you weren't coming to the cat appointment. He said "I couldn't get up." Well he gets up for work every other day because he has to. No apology, no nothing. All he had to do was show up at my place sometime on Friday night and pass out. That's it. Not only did he not do that, he acts like he is too busy to communicate with me or apologize. It's one thing if he has trouble managing his time and his life, but he has no sense of how to communicate with someone when he over-commits or lets them down. Why should I be understanding of someone who is so disrespectful and rude? Why am I still in this?