I went on The Pill about 2 years ago to calm down my periods. They were regular, but gave me absolutely awful cramps, made me feel sick, and I was cooped up in bed for a week of every month. Not good.
Now i'm on The Pill, i'm as regular as clockwork *touch wood*, have cramps, but not nearly half as bad, and they are shorter and less heavy.
Side affects aren't bad; i've gained weight slighty, but i'm slim anyway, so I just filled out a tiny bit, but i'm the only one who noticed lol! Boobs got slighty bigger but not much, which was a dissapointment. Nothing apart from that!
Go to your GP *you can request to see a woman if it makes you more comfortable* and they will check your height, weight, and general personal health, and prescribe whichever pill she/he thinks will suit you best. Make sure you explain thats why you want to go on it in the first place though.
I'm sure your mum will be supportive if you tell her why you want to go on it. Even if she thinks you're doing it as a form of contraception, it shows you want to practice safe sex and aren't stupid.
Good luck!