Breastfeeding and pregnant? What symptoms to expect?

I think I may be pregnant but I'm not positive. I have pregnancy symptoms with the exception of some due to breastfeeding. I know some of you are thinking breastfeeding is birth control, wrong. I was told at my 8 week pp checkup my ovaries were working again although I'm exclusively breastfeeding . Very odd, but true. I have had three normal periods and this month, I was late. I started feeling some symptoms prior to missing, but wasn't sure if being abnormally tired was due to sleep deprivation from my 5 1/2 month old catching up to me or something else, if my nausea is just from coming down with a bug, and nipple sensitivity due to a possible tooth emerging in by daughter? So...three days past the missed period, the pregnancy tests are reading negative. I'm not sure if breastfeeding would interfere with some of the hormones released to be read by the pregnancy test and I just need to be patient and wait a few more weeks...Has anyone else had a similar scenario and can give some much desired insight. I would like to use my free resources before making a doctors appoint which I'm sure will be advised ; ) Thank you so much!