I'm a songwriter/singer... I know lot's of music technicalities and can hit pitches but I still sound nasally!

title pretty much says it all.. every year i go all the way to the final concert at the florida vocal ociation contests.. Everyone says i sing good but i know that i sound horrible!!!! like i said i can match pitch read music n everything... but after 7 years of musical experience, i STILL can't figure out how to make my voice sound nasally.. its sounds like im singing through my nose!!! if anyone can help.. any tips would be greatly appreciated!!! thanks!