surgery and missed period

So last month Oct. 17th I had surgery for a Pilondial cyst on my lower back/top of bum. I started my period later that day about 3 hours after surgery. This was on time and expected. My period lasted my normal length of 5 days. I have not had a period since. pregnancy tests are negative (4). Yesterday morning my fiance and I had pretty rough sex, then much gentler in the middle of the night. I started a very light pink spotting but stopped. I am wondering if the missed period is from surgery or if there is a possibility I am pregnant.