I have had irritation after sex for several months?

Hello, I have an irritation at the vaginal level, more precisely in the bottom of the labia majora and at the entrance of the vagina. I consulted my pharmacist who advised me to put canesten and polysporin, as well as zinc paste for when I go to the toilet. It's been 2 months already. When I have sex, it's only afterwards that I feel pain. The pain can last for at least a week. It's not the first time that it happens to me, but in the past it went away in a week. I consulted my doctor, but since my irritation goes away after a week or so when I consulted my doctor there was nothing left. She told me to see her again if it happened again. I had sex today and the same thing happened again. My labia majora are swollen and a little red. Also the entrance to my vagina. I don't know what to do, it hurts and the canesten doesn't work anymore.