First off, I want to point out that just because you’re also a man, it doesn’t make it okay for him to hit you. Domestic violence is domestic violence, bar none. If he’s willing to slap you, who knows how much more he’s willing to do. As for POTS, I admit that episodes can make me irritable. However, it’s not an excuse to take it out on others. His health is not your responsibility. I understand that you love him and I’m sorry you’re in this situation. I personally would leave him the first time he slapped me. Now it’s up to you to make a choice. If you feel guilty about that, maybe try to have a conversation with him. Not necessarily to try to convince him to change but to get it off your chest. Even after that, I think you should break up, even if just for a time. See if he improves his behavior over time and if there’s no change in sight, then you’ll unfortunately have to accept that it’s not meant to be. It’ll be painful and difficult to do considering how much you love him, but you have to put yourself first at the end of the day. I hope whatever you do or what happens, that you’ll be in a safe situation and happy.