While your boyfriend being grossed out by your period is a bit immature, especially at his age, I can’t fault him for not wanting to continue. It’s blood.
Some people get squeamish at the sight of their own blood from papercuts. And blood is not a normal part of the sexual experience. So I’m not mad at him at all for that one. Perhaps he shouldn’t have been uncomfortable for the whole day, but I’d have stopped as well. My wang is not a big fan of blood on him. It just not a good look.
Hell, it might scare the hell out of you at first.
Now, you feel leper but some of that is your own pride because he was uncomfortable with something that isn’t that crazy to feel uncomfortable about. Step out of your own feelings and realize that its not that crazy. He also needs to let it go too. You all both need to calm down and have a Coke and a smile.
Can’t lie, while it would make me stop, I’d do a fist pump to welcome your period into the equation! At 28, he should be excited every time your period does show up!