Help Please!

Vi

Hi! Ok last month I was supposed to get my period on the 05/19/18 and my period was late because of that I took pregnancy test and came back negative even went to my doctors negative. My period finally showed 05/21/18 and is usually 4 to 5days long this Time was only 3days long 1st days was light pink spotting second day was normal not to heavy or to light and the 3days it was just spotting and done. So I thought it was stress or something. Now this month I was supposed to get my period on 06/19/18 and once again my period was late got it 06/22/18 and same thing all over aging 3days long light spotting first and last day and not so heavy or light on the second day. I’m never late and I mean never. Can someone please help me out has gone thru something like this or know what can it be?