My periods were irregular too. I could usually tell when one would start because I'd get cramps.
The doctor prescribed ibuprofen (600 mg) to be taken before the cramps started. That was difficult to do because my periods were so irregular. Ibuprofen is for the pain but it also helps with the way your body reacts to having periods. It seems like my periods were easier to manage when I took it.
Not only were my periods irregular but some months they were so heavy I wore 2 tampons and a pad. In college I was walking across the quad right after having put in the tampons and was wearing a heavy duty pad and the blood was running down my leg. When the period was heavy at the beginning they didn't last as long as when they were light. But they were still around 7 days long.
Lighter periods sometimes lasted longer with just a small amount of bleeding each day. I could wear panty liners.
My periods did interrupt my life often. Some months I had to stay home for a couple of days. Needless to say my boss didn't like that and wasn't very understanding. A few days the blood went thru my clothes onto the outside while I was at work.
As I grew older the doctor found that I had fibroid tumors. Fibroid tumors can cause irregular periods and a copius flow. I also had endometrioses which also causes the same.
When I was going thru this the medical field didn't know much about endometriosis and weren't concerned about small fibroids. They said I'd just have to live with it. I was so glad when I had a hysterectomy in my 40's.
Yes, it's "normal" to have those sorts of periods. But, today, doctors can provide help to reduce the intensity of discomfort if you have fibroids or endometriosis. But getting a diagnosis is expensive. For the endometriosis I had surgery, also expensive.
Have you seen a gynecologist? Doctors are much more knowledgeable and sympathetic than they were when I was your age. There may be something that they can do to help. YOu can go to a county clinic which charge on a sliding fee schedule.
The BC pill did regulate and lighten my periods. There are lower dose pills available now. I thought the risk of taking the pills wasn't as important as getting control of my periods. I did stop taking them, on my doctor's advice, in my late 30's I think.
Re: IUD's They tend to cause cramping. My daughter tried one just a few years ago and had to have it taken out. I don't know if it was the Mirena. Back in the day of the old IUDs the doctor said I wasn't a good candidate for one because I already had severe cramps.
One thing that helped me manage the flow was the diaphragm. It catches a fair amount of blood and used with a pad was effective for me. After my hysterectomy a friend asked for my diaphragm so that she could use it for periods. (she was in medical field and knew how to sterilize it.) Of course this is messy. The first couple of days I had to remove it and reinsert it 2-3 times.
For awhile there was a cervical cap that you could purchase OTC which helped but I don't think it's available any more. I liked using it because during the last days of my period that is all I had to use.
There is a BC pill advertised now that claims it helps with mood changes etc. It's called Yaz. Because it has a lower dose of hormones you might want to try that. The only time I had more regular easy to manage periods was when I was on "the pill."
I sympathize with you. These kinds of periods are a pain in more ways than one.