what could it be?

so im 22 yeats old and have endometriosis. Been trying over three years to get pregnant. For the past couple weeks my nipples are so sore that anything that touches them causes me horrible pain and ive had the worst cramping in my stomach and overly nauseous everytime i eat or dont eat. I'm a couple days late for my period but I've been late before but not recently. I wish it was because I'm pregnant but because I've been let down so many times I don't think that's the problem. So I'm curious, what could it be?