Hot Flashes- POTS, hypothyroidism, or something else? (Minor nsfw)

For reference I (f22) have already been diagnosed with POTS and hypothyroidism and I’m medicated for both (levothyroxine, midodrine, metoprolol).

I’ve noticed that the past 4-5 times I’ve started to get in the mood with a partner, after about 20 minutes I suddenly start to feel super nauseous like I’m gonna vomit- I actually did 2 times and it was super embarrassing! My primary doctor swears my thyroid is balanced but I have to question why someone my age is having such bad hot flashes that they’re nearly puking just from f*replay. Someone please help me, I feel like a broken body