Help a girl out - pregnancy questions.

So I hear cramping as long as there is no blood and it isn’t worse than your period cramps is normal. I’m estimating that I’m 3 weeks 4 days. But why does a tight waist band on my pants bother me so much. It feels so full and tight in that area.

I’ve never been pregnant so I have no reference for myself and don’t know what’s normal.

Edit: I also have a fibroid in the posterior wall of my uterus diagnosed by ultrasound in July 2016. I have not had an ultrasound since. Would this also impact the full feeling ?