What Causes Delayed Period?

Hi! It's been 39days since my LMP. I took 4pregnancy test at home and it all came out negative. My partner and I trying to conceive and my doctor gave me Clomid and took it on the 2nd day of my period for 5days. We did tried to have sex everyday since jan 1- 18 and my partner went back to London jan 19. Until now I have no period but having pain in my lower back hip and lower left side abdomen. Having headache and my BP increase to 137/75 and constantly peeing 12-15x a day and boobs sore for 1 week now. I'm 37yrs old and I know that chances are quite small for me to get pregnant. But were still hoping to have a child again. We got 3kids already. Could you pls let me know if there is a possibility that I'm pregnant. Thank you very much for your help.