TMI- irritated vagina- 27 weeks pregnant

Maybe a little bit TMI but I don’t know where else to post this. So today is Monday, my partner and I had sex on Saturday morning and he came inside me. (I’m already pregnant so 🤷🏼‍♀️) I noticed this feeling a little bit yesterday but more so today, my vagina is a bit swollen and very red, and hurts (almost burns). I also have red bumps around my labia. Any idea what this could be ?

There is no way it’s an STI because we have literally been together every day for the last month 😂 we have had sex lots in the last few months but this feeling is new.

Could his hands have been dirty when he started to pleasure me ? Could it have been my underwear ? His cum?

Any info is appreciated, please be kind.