If you are always tired you might want to get your iron & adrenals checked. There are ways to check, informally, for symptoms, as can be found on the net. Urine test are far better than blood tests for adrenals.

The Zapper Forum will answer many Qs on zappers.

A biting sensation in the feet can indeed be symptomatic of parasites in that area of the body.

A sensation by itself isn't enough to come to a conclusion, though. How do you know it's not just nerves firing? When's the last time you had your fasting blood Sugar checked and had general blood work done (e.g. CBC with CMP-14)?

Try soaking your feet in water as hot as you can stand it with liquid laundry detergent, borax and apple cider vinegar. Try to keep the water hot for at least 30 minutes. When you take your feet out, dry them off and put coconut oil on them. This helped me get a lot of something out of my feet. I still don't know what it was. It came out of the cracks in my heels and looked like little hard disks, and came out like grains of sand on the balls of my feet. I got the treatment from the Morgellons forum. They use it for soaking baths, but I just did my feet. I had to scrape the stuff that came out off of the bottoms of my feet. I did it every day for a week, and they didn't come back.