periods and spotting three times in one month

so I had a very abnormally light periods (pinkish not exactly red) July 30th until August 2nd so three days and just enough to barely even go on a pad then I spotted again the 8th to the 10th. same thing now I woke up today the 21st and spotting again I have been trying to conceive for only 4 weeks & I've taken two pregnancy tests already and they're both negative so not quite sure if my cycle Is just really off . if im spotting or implantation bleeding? also my symptoms are mood swings night time I feel very dizzy and nauseous and also having back aches and migraines I don't have a regular cycle so all I can really do is take a test every week but bleeding three times in one month or spotting pink I'm not quite sure what is going on any suggestions or answers are appreciated