Burning after intercourse

Hey all, so pretty much every time after sex my labia feels swollen and burns. It's only lasts about 15 minutes to a half an hour but is very annoying. We don't use any lubricants because we are ttc and I've heard that can make it difficult to conceive. I've been to the doctor for testing and everything comes back negative. Just wondering if anyone else has experienced this and if so what you did to help? Thanks!