Do you have a plant in the room? We have a plant in our computer room and sometimes I start feeling gnats or mites around me. Sometimes I see them sometimes I just get feelings as you are describing. I put a drop(just a drop or two-too much will kill the plant) of liquid dish detergent in the water and water the plant. This kills off the gnats. I learned this from my mother.
So, if you have a plant, give this a try.