Well, in my opinion, you should know that this situation is kind of normal. So you should not too worry about it. First, as we know that the light is so strong that when we open our eyes to see it, it will just make the eyes hurt. And also our eyes are so very sensitive that they will react to the stimulation from sun light. So when the sunlight gets into our eyes, it will make our eyes to adjust to it. Sometimes, it will also make your eyes not just hurt, but also become watery. So at this moment, you'd better wear sunglasses to protect your eyes from the strong light and the UV rays. And also, there are many dirty objects in the air outside, so when you go out, your eyes are easy to be infected by them. Just be careful about it. Anyway, you should not make your eyes to be exposed under the sunlight for a long time.
When sun rays are bright, you should know there is sun radiation. When eyes are exposed under sunshine, the eyeballs are sensitvie with any sun radiation, obvoiusly it can not endure. Since you often go outside, your eyes can not bear. Therefore next time, you better squint your eyes when go outside and if sun rays are bright again.
If your eyes are normal, they will not feel hurt under the bright sunlight outside. Your eyes may get the inflammation because of the bacterium. You should go to the hospital and have a full check on the eyes as soon as possible. Or your eyes may get serious which may get watering with no control.