Bloating and swelling immediately after sex?

I have yet to find a direct answer for this question, and I see that other people have experiences it, but have received no real answers for it. Every time my husband and I have unprotected sex, almost immediately after I feel bloated in the lower abdomen. This happens every time he ejaculates in me.

And this time I'm a bit nervous because I've been off birth control since September because my prescription ran out, and I couldn't go back to the doctor until a few days ago, but since I haven't started my cycle yet, I'm still not on the pill yet. My husband, through a misunderstanding, believed I'd started the pill, and we had unprotected sex yesterday, and he ejaculated in me. I washed myself out in the shower immediately, but I still got bloated. I'm wondering if this immediate post-sex bloating feeling is normal. I know that this is one of the signs of pregnancy, but this happens every time we have unprotected sex, and it's too early to know if it's pregnancy related or not. (I really hope it's NOT).