How often do you and your SO have sex on average

So last night I told my boyfriend we would have sex before we went to bed, eventually I got stressed out from studying I was no longer in the mood. Tomorrow is my last day of the semester and I have two finals. & he said he was going to bed, and apparently he said I said well I guess we can't have sex then, so he waited a little longer until I went to bed thinking we would have sex. He got an attitude saying I'm always like that and he doesn't want sex tomorrow and how we shouldn't have sex anymore (he doesn't mean it but still). I thought that was super inconsiderate trying to make me feel bad when tomorrow is a stressful day already! I told him it was simply a misunderstanding and shouldn't make such a big deal about it & can have sex tomorrow ( because we are going home to visit our parents so wouldn't have sex until some time next week again). We had sex on Monday and he's making four days sound like it's a huge deal to our relationship, when we have both been busy with finals! (We live together). I always thought of myself as a sexual person, and then this relationship really got the best of me making me feel bad about not wanting sex all the time. I never experienced that before. We have been together for two years and this topic has definitely been one of our top fights throughout that time.