I'm due on 24 May too (I use my dates, not the scan date) and I have been a rage monster this week. So maybe that is it.
cant I think between now and birth our babies are going to nearly double in weight so it's no wonder you're getting more tired. They're using up more of our energy and making us heavier. Plus I think the hormones for birth start building up too, so that's a lot going on. Certainly my joints are starting to feel more lax, and that's part of getting ready for birth.
Re chubby babies: DD1 was a little chubby but behind one clothes size till she was 2 1/2, at which point her legs shot up and she looked even skinnier. DD2 was ahead one clothes size till she turned one, and she still has her super gorgeous chubby little thighs. DD1 was 7lb2oz; DD2 7lb15oz, so neither of them big at birth. But DD2 fed All. The. Time.