21 Days Late! 3 Negative Test

My last period was February 19. I have had cramps here and there since then. On April 4 while at work, I got this really bad headache, my body felt weak, and I threw up. I went to the hospital and they gave me a pregnancy test and it came back negative. I’ve taken to at home test since then, both negative. I just recently started having breast pains and sharp pain in my back. My bf came home from basic training in February so there is a possibility I could be. What should I do?🤔