are u familiar withthe song? or did u just take one of the suggestions made from the guys here? if so the song might be totally new to you and ur not as familiar and comfortable with it...take a few breaks try to get the timimng right...as for singing i think it just needs pratice...dont give up yet mate cmon!..you can also try playing along with the song first i think...
just my 2 cents!
[FONT=Impact]grooviest tunes ever [/FONT]