Sorry to hear you feel so cruddy! This is pregnancy #1 for me and there have been times (in the 1st and 3rd/ current trimester, mostly) when I felt weaker than I ever have in my life... it's a very strange feeling! Can't imagine being that way with a kid(s) already
I did find that eating a ridiculous amount of protein helped me somewhat - like, 3 eggs in the morning, a proteiny smoothie after lunch, etc. I still get very tired and that weak feeling but it doesn't seem to be as intense or hang around as long.
Also, avoiding sugar (which I am still struggling with!) and refined carbs and grains, particularly before the evening, seems to help. When I can do it
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My iron was low and I felt it in a big way. Taking an iron supplement has helped though I don't think I was even that anemic. I also started taking vitamin D3 and that seems to have helped too.
Lots of things add up to a slight difference. I wish I could say I felt a big surge in energy returning but... some days and times of day are better than others. Good luck!