Tonight my SO and I went to a local community non-profit that is open 24/7. He was going to work on a project, but I had just gotten off work and was tired, but I didn't mind going. In fact I usually enjoy going here, but this time I was mostly just going to wait for him to finish. We got there around 9PM. At 10:40 I went to find him, feeling very tired now with an upset stomach. I asked how his progress was going, and if we could leave soon. He said if we left then he'd have trouble finding his place again, and we agreed to leave at 11:30. Well this time has come and gone, and I go to find him at 12:15. He is still working and lost track of time. I'm annoyed but don't make a fuss. He starts getting his things together. By the time we actually leave it's 12:40. He notices I'm not my usual chipper self, I haven't smiled, etc and asks what's bothering me. At first I try to play it off and not say anything, but he asks again so I tell him I'm a little annoyed we're leaving so late. He responds dismissively, asking why I'm making a big deal out of it, and this pisses me off - I snap at him and tell him not to bother asking if he doesn't want to know what's bothering me. He asks why I'm acting like this, it's not like he did it on purpose, and how I don't "normally" get so upset when he's late. I said I know he didn't do it on purpose, or I would be a lot more upset, but it did hurt that he would be so inconsiderate as to not check the time at all, especially since I had already told him I wasn't feeling well and wanted to go home much earlier. He says he's sorry we're leaving so late but he didn't do anything wrong b/c it was an accident, I can't be mad at him for losing track of time. I tell him it was thoughtless and inconsiderate, he says I'm implying it was intentional. I tell him he's blowing it up and he's the only saying anything about it being intentional - I was upset based on it being an accident. I'm getting more upset b/c of 1. He was thoughtless, but that was a small amount of upset 2. Instead of apologizing he insisted he had nothing to be sorry about. We argues the whole way home, to the point where I said I was tired of debating, neither of us were changing our minds and I was tired of him trying to convince me that I was wrong to be annoyed. 

Another bit of information - my birthday is this Sunday, and we're going out to dinner with my folks. We've been together for 6 years, but he's not doing anything for my bday, no present, no date, no anything, the only reason I'm getting any kind of special treatment is because of my folks. I'm trying not to show my disappointment, trying not to feel selfish, but I think I lashed out at him b/c of these feelings. However, I still think he was inconsiderate tonight. What do you guys think? Am I the asshole?