Is it still possible

I'm 11dpo, AF due in 4 days. Since 6dpo I've been feeling really nauseous and thought I had food poisoning. Last night till now it has eased a bit, but I'm still getting cramps in my uterus and lower abdomen. I've had no other symptoms. Took a test this morning (fmu) and bfn. I'm starting to get worried I may have endometriosis because I've NEVER experienced cramping or nausea like this leading up to AF. Is it still a possibility I could be pregnant?