Has anyone here worked out through their entire pregnancy and can give me some insight?

I was fit & very active before I got pregnant, my doctor has given me the okay to continue my strength training routine through my entire pregnancy unless any complications arise. I’m 20 weeks and so far i’m still feeling great. I’m not showing a whole lot yet but I’ve noticed in the past week I’ve started to feel a little heavy in my uterus area and a little weighed down. During my workout today (which was nothing new) I started cramping and felt tightening. It went away quickly and I continued but it happened again, and again. I decided my body wasn’t having it today so I left the weights and walked for 30 minutes instead. At what point in your pregnancy did you have to start taking it a little easier on the weights? I was hoping to continue on much longer than this but the cramping/tightening has worried me!