I know I'm very late to this, but I thought I'd add a couple more ideas, in case you still need help.
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ginger. seriously, it's so effective (for me, at least), and relatively cheap. you can even buy it in capsules.
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peppermint oil. I get the worst motion sickness while riding the bus near me. I put just 1-3 drops inside my mask and it helps a lot. you might be able to just take a whiff of the bottle and get some relief, tbh
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it doesnt really sound like this is the case, but do you drink coffee or tea on an empty stomach? I used to be able to, but now the tannins always make me sick. :(
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I would suggest keeping a record of when it happens/for how long, what you ate/drank that day, what hygeine/skincare/cleaning products you're using, how much sleep you got the night before, if it's worse/better certain parts of your cycle, ect. it might help narrow things down.
I really hope your gyno takes you seriously. it sounds like you may need better doctors.