blowjobs....

Right ladies I need your help!! Blowjob tips! My man says I'm good, I do all the right things etc etc but I have never let him "cum" in my mouth. I kind of have a phobia about it as I have no clue what it would taste like, I also have a gag reflex and also my jaw aches so badly which is why I stop but all I want is to allow him to do it in my mouth!! Any tips?! TIA