My neighbor always stare at me, what to do?

Hi! so.. i have a neighbor that Always stares at me when i'm outside walking with my dog. Or whenever i'm outside. I have seen him just staring behind the curtains. This have happen in about 1 year now.
Yesterday i did feel like he stared at me , so i looked in his direction and he probably notice that so he run to the otherside in the house. It is hard to explain tho.. but i just starting to feel uncomfortable. I really want to know the reason, but i don't know how. Because it feels wrong to ask him..
My neighbor always stare at me, what to do?
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