I agree with wildwood, and am allergic to the stings myself. Having said that, I've learnt to spot one a mile off, so try to get out of the way!! : )
It's not an irrational fear that you have, since you received a sting which's made you wary ever since, but fears can then turn into phobias, whereby everything about these insects is taken way out of context.
Bees, in general, won't harm you unless they're threatened in some way - such as trapped in clothing. Wasps, because of their ability to sting more than once, will do. I think they're of a more aggressive nature because not only do they help to pollinate, but they're nature's scavengers and probably have to fight for food, so their stings are used to kill other insects. Hornets, on the other hand, can sting painfully, but the amount of venom is quite small, and only someone who's allergic to this would need immediate medication.