Irregular periods

I so starting the new year I came on my. January 19th 2016 I spotted for 3 days and then it picked up heavy for 5 then in February I started seeing spotting on February 12th light spotting once again barely bleeding not having to wear a pad at all then after 3 days of that it picked up heavy for 5 days ok its March is not time for my period yet but never in my life of 30 years have I experienced this has this happened to anyone else I also took two pregnancy test two weeks apart and both of them said negative