I have been wondering, am I still just adjusting to having a regular flow, or is something a bit off =/

I will be turning 17 in about a week, but I started my period right after I turned 11. For the first year, my periods were light/normal w/ no clots and lasted only a few days, and happened every few months. While I was 12, my periods became about a week, and became kind of heavy and had some clots about walnut size. I was only getting them 3-6 times a year. When I turned 14, my flow became a bit more heavier (having to change a Super Plus tampon every 4hrs), and every once in awhile I'd have a clot about the size of 2 walnuts. My periods were like that until about my 16th birthday and happened 6-9 times a year, though sometimes they ran for 2 weeks (I guess from skipping some months?). Over the past year, my period has 10/12 months, and has varied in heaviness. Some months would be a regular flow with minimal clots that would only need a super plus tampon to be changed every 6hrs or so and lasted about 5 days. However, some months I had to miss school because I would pass a clot 3/4 the size of a tennis ball every 1-2hrs for about a week. Over the past 3 months, my periods have been like the latter, and it's been annoying. What has caused me to ask my question, am I still becoming regulated or is something up, is my current period. I was reading about anemia, and I started taking Flintstone's vitamins w/ 18mg Iron as I heard they were good for upping iron levels. I started on Saturday morning, and all weekend I have had clots about 3/4 a tennis ball every 2hrs. Just today (I have to go to school because I have finals this week), I soaked through a wad of ~8 paper towels I was using in about 3hrs time. Over the past few hours I've still had clots, but they're about 1/3 a tennis ball now. (It seems since I started taking the extra Iron, my period has been a bit more heavy). I'm up at 3:30am now trying to get a few more out of my system before I have to be in school from 7am-noon, with absolutely no time for a bathroom break.

Am I just having bad luck with my body finding a regular period, or could there be a reason I have been getting annoyingly heavy flows?