Burning after he cums

Every time my boyfriend and I have sex and he cums inside me it burns. He and I are both clean from STDs and such (we already got tested). We have been together for 3 years and for the first couple of years we still used condoms and it would only burn when the condom broke. Sometimes he pulls out and other times he doesn’t. When he pulls out I have no issues but when he doesn’t it feels like someone set me on fire inside my vagina. Is it possible to be allergic to his sperm?