My vagina burns when I have sex but only when my boyfriend finishes inside of me

Ive been with my boyfriend for 6 months and he usually doesn’t finish inside of me and I havn’t had any burning sensation when using condoms or when he pulls out. But everytime he finishes inside of me the inside of my vagina starts burning and sometimes my pee does too. The burning usually goes away away 30-40 minutes but it’s still a pretty intense burn. I’ve had sex with other people before but I’ve never had this problem when they finished inside of me before.