Plain unfortunate when these things happen and sorry to hear it got you down so. But it’s also wonderful to hear from someone non-judgemental: appreciating this guy for who and what he is without trying to impose your expectations of what you think he should be.

I too suffer from menstrual problems but in a slightly different way so I can appreciate the wild times and how they affect others particularly men. Unlike Anne in a post above I don’t think it’s conditioning. It’s more because they simply don’t experience the thing. Some men do seem afflicted by periodical cycles but a lot less.

However, I go along with what others have said. Depressed though it made you he is a guy who meets his commitments. Steadfast. And in a way you have to wonder about if the boot were on the other foot: say, he was with a friend before joining you who was seriously upset about something – would you have appreciated being “stood up” because said friend demanded he stayed?

And of course the other thing is how well you could communicate your feelings about yourself; what you think was the cause, whether this was the monthlies in which case you’ll have some measure of yourself and can at least know what's going on.

I sincerely hope that as the hormones subside that this will be over and that you can resume as normal what sounds like a very good relationship but with increased awareness of how it affects you in the future.
All the best.