Why Are My Menses Lasting Longer Than Usual?

Good day, I've been on the pill 3 times, and quit. It never had a side effect. But last time I quit, around the end of 2010 my periods started to get longer. Regularly they'd be every 3-4 weeks for 4-6 days (since I started getting periods, around 6 years back) but each time I get one, I have to wait longer, and the period only lasts for around 3 days.
I'm really worried!