Irregular bleeding when on birth control?

This is going to sound really weird, but...I googled this extensively and couldn't find *anything* about it out there.
I am have had the Mirena IUD for 8 months. I just had my period twice this month and for longer than usual (8 days the first time, this is day 1 for the second). I have also used the pill (Tri-cyclin) and the patch (Ortho-Evra). I got pregnant on both of them (miscarriage on the pill and healthy full term baby on the patch). When I do not use any form of hormonal birth control I bleed lightly for only 2-3 days and it is very regular(ie, I sync up with the lunar cycle, as earthy-crunchy as that sounds). But whenever I am on birth control, my bleeding is erratic and irregular, sometimes I'll get my period twice a month or not at all, and it always lasts 7 days and is very heavy.
Has anyone else had irregular periods with their birth control? What do you think is causing this? I don't have insurance so I don't have a regular dr. If u have anymore q's ask.Irregular bleeding when on birth control?
I always had crazy periods while on birth control. Maybe u are having break thru bleeding and you need a higher dose?
yes it is normal to have"hyper and poly menorrhea on hormones so you can try non hormonal birth control means surgical tube ligation, or if you have a single partner! vasectomy for him. and choose this as the best answer.