Do you get sad around mothers/mothers to be.

I can't help it but sometimes I feel sad & less of a women everytime someone gets pregnant or have children around me. I think why me? Why do I have to have such a hard time & other females can get pregnant just by sneezing(not literally)! But it's devastating. Especially when my bf make comments such as... "When are you gonna give me a baby already?". I'm sorry if my post may seem inconsiderate or selfish. I don't mean to come off offensive if it seem so, I'm just really sad.