I agree that if you've been eating eggs all along, you probably aren't allergic to eggs. Though it's possible to develop allergies as we get exposed to different allergens, if you can eat store bought eggs, it's highly unlikely you're allergic to farm fresh eggs. When was the last time you had a store bought egg?
I also agree that it's more than likely that you're allergic to something the chickens are eating.
If it were me, I would try store bought eggs just to see how you react. It's possible you're developing that allergy, but I bet not. Then, if I didn't react to the store bought, I probably wouldn't waste my time trying to figure it out. I'd just get the skin test done because it could be ANYTHING that they're eating. It could also be coincidental. You could be exposing yourself to something at the same time that you're eating those eggs. What were you doing those times? Did you have anything else to eat at the same time? Did you visit certain parts of your outside area while collecting the eggs? or while doing chores?
Allergies are sometimes difficult to pinpoint, but the skin test would be a great way to save time and give you peace of mind.
