40+days since last period

I have been on the depo for 4years about and I stopped the shot. My last shot was on September 3rd. I started my first period on January 25th it was really light and brown in color but lasted 5 days. It has now been 45 days. On the 44th day I did have sex and their was a little spotting but it lasted for a few hours after... Has anyone ever had this problem I have take. Several pregnancy test all have come back normal I have even went to the dr and took a urine test their and negative.i am going on 3/15 to request blood work. And I have been feeling really bloated and constipated. Also I would like to note I have had thyroid cancer in 2012 and had two radiation treatments and had my whole thyroid taken out in 2012.Me and my husband are trying to get pregnant. I feel like taking a test everyday is a little much but I need some insite... Please if anyone has been in this situation and could help with some input that would be great.