I used to feel nausea at let down in the early months
It might not hurt to get a checkup and some blood work done, just to see if anything's off.
A thought about the water... Something that worked for me was, rather than making myself drink more, I keep a big glass of water next to me at all times during the day. It's just a slight mental shift from "I have to drink more water" to "I'll just keep this bottle/glass here and put water in it whenever it's empty". A sip now and again all day long can really add up without it feeling like you're forcing it.
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