I've been told by a gynaecologist i shall have to take the contraceptive pill in at a high dose to bring back my periods. is this a common way to treat?

Not usually: A normal pill today is 30 micrograms of estrogen. That should be enough to control your periods , and patience for 3 months is needed to get regular. Take the pill at the same time of day each day. Don't switch pills at shorter than 3 month intervals. It's unusual for a 19 year old young woman to have physical problems, but screening for infections that might make your cervix blled would be good.