Hi, I Am 29 And Have Had Normal Periods Of

Hi, I am 29 and have had normal periods of 28 day cycles since I was 12 years old. I had a tubal ligation 14 months ago immediately after my 3rd c-section. Two weeks after my last period, I started having very light brown discharge and over the past 9 days it has continued in the same amount but has gotten darker. I have been really nauseous at night and have had slight cramping a couple of times. I have had an occasional sharp pain in my lower left abdomen. Could I be pregnant? I haven't taken a HPT for fear that I am.