Period has changed

So for the past 2 cycles my period has changed so much. Day 1 very light, day 2 moderate bleeding followed by brown blood, nothing on day 3..day 4 and 5 very very light. Also the bleeding on day 2 is very pale red. I used to have quite heavy periods so I'm just wondering what would change them so much? Would there be something wrong? I suffer horrible PMS and even now on day 3 im still cramping and feeling nauseated fatigued and have a terrible headache. Would it be worth a visit to the doc?