What Causes Delayed Periods Along With Sore Breasts And Headaches?

had a period onFebruary 8th thru the 12th normally and then another one came February the 27th and went off on the first of March and I haven t had a period since my breasts have been sore light headache constipation I took two pregnancy test and it came back negative today makes 5 days late.. I ve been gassy