I am 16 i have had white-yellow discolouration on my toenails for around a year, some nails are thickened, soft nail peels off, am quite concerned?

Nail fungus: sounds like onchomycosis, a picture would help, the treatment is oral lamisil (terbinafine) for 2-3 months

No Fun Fungus.: More than likely, you have been hosting a fungal (mushroom) infection in you toe nails as well as nail roots. Clearing this up is going to take some time and direction. Topical treatment will probably not be sufficient . There are several oral medications available and your family doctor should be able to prescribe the most appropriate for your particular circumstances.