could I be pregnant?

Two years ago I went for tests with doctor to see if I was ovulating and they said I wasn't but I'm unsure if I am now. My last period was on 3rd October lasted about 4 days. My next period was due on 31st, on Tuesday I took a pregnancy test and it came up negative. On Wednesday 2nd I had abit of spotting but no red blood. It was on and off all day, light pink blood and never got heavy. I woke up this morning to abit of browny blood on tissue I had down there, as I thought I wasn't heavy enough for a pad. I have had tissue down there ever since just incase but have got nothing. Could it be implantation bleeding or am I just having a really light period? I'm starting to get some cramps, and boobs have been sore for past two weeks. Please can people give me advice. Thank you