Please please help me - I've never been so dissappointed! :'(?

Not a great idea, i wouldnt adbise it, and Im not some old person, im just 15, but trust me, your too young to know what you really want, hell, even im too young! You may regret it when your older, plus it leaves a hole there, which looks kinda gross. Wait until your 16 or 18 so you can decide properly for yourself, without any peer pressure or anything. And your mum is right, they do look trashy, plus you have to have a completley flat stomach at all times, which trust me, gets harder as you get older, and you cant wear any fitted tops cos it can poke through....so do what you want, but i personally think that you should wait a couple more years so that you can think for yourself.