i guess i either have a very small mouth or my bf is well endowed...i think it could be both but most guys want to be able to touch the end ..i guess it feels good to know you can reach that far AND the feeling i guess feels good to...but i gag alot too...im getting better but sometimes he still gets...fiesty...so what i do is i curl my tongue to the roof of my mouth and he ends up hitting the bottom of my tongue gets the pleasure and i dont gag...plus sometimes i use the inside of my cheek at times for the same effect...

also concentrate on other "areas" ...if you dont want to give a full bj how about tickling and exactly using your whole mouth just light biting ...and stuff like that...sorry if its too graphic..i dont know how else to put it.....good luck...also use some yummy products that youd want to eat lol...like a good tasting frosting..or whipped cream, hot fudge, melted chocolate...not only does it taste good...but he will definitly like it
or if you just dont like it and dont want to give it..then just say so ...if the guy is close to you and actually cares (which i hope he would) then he should understand and not force you to do something you dont wont to do...
good luck
love,
inny