My husband has wanted this for years and I finally said yes and now I cant breathe

im writing this at 2am in the spare room because I cant sleep next to him without my brain going feral. bit of context. F41, him 43, together 15 yrs, two kids who are now teens and basically ignore us which is the only reason this conversation even started. about 4 yrs ago he brought up the lifestyle, very gently, very "no pressure just wanna talk about it". I said no. like a hard no. and he was completely fine with it, never brought it up again unless I did. we've talked about it on and off since then, mostly when I bring it up after a glass of wine and then panic the next morning. three weeks ago we were on a weekend away just us two and I said the words. "ok lets actually try it". he didnt jump on me about it which I appreciate, he just said "really? are you sure?" and we talked it through and made some rules and I felt great. proud even. like Id finally caught up to him. now we have a meet-and-greet thing in 11 days. its at a quiet bar, just drinks with another couple we've been chatting to online for a few weeks. no expectations. and yet I am LOSING IT. like physical symptoms. tight chest. wake up at 4am. cant eat lunch. heres the bit i feel stupid about. i think a part of me is angry at HIM even tho he hasnt done anything wrong?? like i agreed, i picked the couple, i picked the bar, and yet my brain is going "this is his fault". i dont actually believe that but the feeling is there. is this normal first time stuff or am i just not ready and trying to please him.