Hi, I Am 28 Days Late On My Period. I

Hi, I am 28 days late on my period. I have taken several urine pregnancy tests, all negative. On October 21st, I also had a negative blood pregnancy test. My OB-GYN prescribed me Meddroxyprogesterone and I took the medicine twice a day for 5 days (October 23rd-27th). Today is my 11th day off of the medicine, and still no period. Can I be pregnant? My husband and I have been trying since mid-August. My last period was September 11th-15th.