My (42F) boyfriend (42M) completely forgot about me.

This past weekend, my boyfriend of 11 months invited me to stay the night with him. We both work during the week so we usually see each other on the weekends. He called around 10 am. and asked me to be at his house around 6 pm. So I spent the day getting things done around my house and also getting ready to go to his. He did mention at the time that he had some errands to run and would let me know if anything came up. Well I show up at his house at 6 pm. like he asked, only to be met with an empty driveway. I called him a couple of times, and he did not answer. At this point, I am mildly concerned. Maybe I didn't hear him right. Well, I sat in his driveway for over 30 minutes. and finally decided to head home. I am a little upset at this point. I texted him one last time that I was leaving and not very happy. I wasted so much time to get ready and come over only to be left sitting there. He then proceeded to ignore my calls and text. After another 10min. of sitting there, he texted back that "He told me he would let me know if something came up, and that's my bad." I was quite taken aback at how casual he was about it. He then ignored me for the rest of the weekend and only called me back Sunday night. I feel like something is very off about this whole episode. I now feel like he was doing something behind my back. I am very much upset about him forgetting that he invited me over. He has since downplayed the whole thing and repeatedly said he is sorry. In my mind, I have no idea how you just casually forget about your girlfriend coming over. He told me he was at his cousins house doing some work and ended up staying because it was so far away and he had been drinking. I can not for the life of me just forget about how he didn't even bother to feel bad about what he had down at the time. I have never felt like someone didn't care about me, but now I do. Am I crazy for feeling this way. Does anyone have any suggestions on how to approach this matter? I still feel completely blindsided and hurt. How to you get over something like this? Would you stay?