i had pretty bad cramping from 4-7 weeks, they ended last week pretty much completely.
i was really worried even though everyone told me it was ok, i finally went in and got a u/s at 6w4d to double check everything and it was totally fine just like everyone said.
they said that of course it was the uterus stretching and also the corpus luteum that sticks around for the first few months to product the much needed progesterone
i totally understand the worry, not much can calm you, just want you to know that so many of us have been there just like you