Hi and welcome to the forum. This is a great place for advice and support. I'm sorry to hear that your boyfriend is having a bad day. I think that you telling him that your not going anywhere was great.
Flare ups can be very painful, and from what I understand everyone responds diffrently and painlevels can also be diffrent. For you the best thing is to allow him to rest and give as much support as possible.
When someone is going through a flare everyday things like brushing your teeth for example can be painful.
He may feel bad that he can't do more. I think sometimes it isn't always about what you say to the person that matters it's really about just being there and showing compassion.
I truely hope that you find the advice and support that you will need as well. This forum is a great place to vent and ask for advice. I also hope your boyfriend starts to feel better. We are here if you need us