I was going to say something similar to what DigitalSweety just said. Work on getting used to just being down there. My husband loves it when I lick him all over...it feels just as good to him as when he's in my mouth.
Don't worry about going too far in your mouth, keep a fist around the base of his penis while he's in your mouth, and you can even stroke while your hand is there. This will prevent his penis from going too far into your mouth. Your lips will only go down to your fist, no further.
Adding a flavored lubricant might help too. Focus on tasting the lube and nothing else. There are loads of options available here that could help with that. Also, are you watching what you're doing, or keeping your eyes closed? I find that keeping my eyes closed helps me to focus better on doing a good job and less on what's happening.
I have never tried any type of throat numbing stuff personally, but I've heard a lot of people say good things about them.
I hope this helps..if you have any questions don't hesitate to ask!