my bf had a panic attack during sex

i’m bisexual and my boyfriend has always kind of had a hard time with it because his ex left him for a girl. recently we had a threesome with another girl. some rules were put in place including that she other girl didn’t want him to penetrate her. at first she was really nervous due to past trauma but once she was comfortable i started to finger her and we ended up scissoring while i gave my bf a hj. at one point the girl and i were making out and moaning and he started to have a panic attack and had to leave the room. i feel so so so awful about it. he claims he’s fine and has even been talking about doing it again and how much he wants to but i don’t think he’s ready. idk what to do because i really want to do it again because it was so hot but i am really worried about how he would react this time.