Maybe allergic to my boyfriend

So something that I’ve noticed in my relationship is that every time my boyfriend and I are intimate with each other without condoms and he cums in me I swell up and it burns like all hell and we both have been tested and are clean across the board. Witch leaves me with this big question could I be allergic to him? And if so how do I talk to him about it because I know he will take it well, however it’s embarrassing on my part. Can anyone help me out or do you have any tips or advice.