Low iron and protein in urine

So I'm 37 weeks tomorrow and today at my doctor appointment my iron had gone down again (from 12.7 to 9.9)(I don't know why) and I have some protein in my urine (not a lot at all) but my blood pressure is normal. What else can cause protein in your urine? My doctor just told me to drink more water and said I'm fine but I'm still worried. Ftm here.