Help please

Please bear with me. I need help.

Me and my bf had unprotected sex last september 14. I am now 13days late (49th day of cycle) We also had sex last september 21st and 28th all unprotected. I took hpt 3x and it all came out negative... i had tvs ultrasound last october 3 and i have polycystic left ovary and thickend endometrium (14mm) and still negative on hpt when i tested again yesterday. Could i still be pregnant? Or is it because of hormonal imbalances. If i am pregnant wouldn't it show up on he ultrasound already? I'm worried right now. I'm not ready to be pregnant but i'll take that instead of a possible disease. :(