What Causes Light Pink Spotting Instead Of Regular Periods?

My periods are usually heavy with really bad cramps.Thursday to Saturday instead of a normal period I ve been seeing brown and pink tinged mucus. Now today is Sunday and I m seeing blood as if my period is coming but it s very light. With my first child I had something like a period, every test I took cand out negative so I went to the doctor only to find out I was 5 months and 2 weeks. Could this be happening again?can I be pregnant