I don't think any sort of sexual act should be a deal breaker. If he cares about you then sexual pleasure should be second, third, fourth etc. on his list, anything but first. Your clearly not comfortable with blow jobs so you should only do them on special occasions (birthdays, special nights away, anniversary's etc) or just when ever you are comfortable giving them. A guy should be able to survive without getting a blow job haha. They feel really nice and can be a very pleasurable experience though so as I said you could possible give them on special occasions as a reward.
Another way of giving a type of oral that you may find slightly more comfotable is, you could always bend down on your knees and and just tease his member with your tongue and give it quick pecks while giving him a handjob