Fundal height measuring 3 weeks behind!

Cheyanne • Boy 3 💙girl 1💜expecting #3 march 2020

OB said im measuring small and asked if i measured small with other 2 kids which i did not. Im kinda worried! she says she'll do an ultrasound in 2 weeks, but i cant help but think i have done something wrong considering this pregnancy iv had a load of stress and taking prozac:/