I feel something biting me at night mostly at my legs what could it be? I don't have pets in my home & now my son feels it too.

The first pest that comes to mind is bed bugs. Go to this site to see if they might be the guilty party: Bed Bug Treatment: How to get rid of bed bugs- BedBug Facts, Treatment Guide, Kits & Products

When you get up, are there any signs of bites... redness, swelling... on your legs?

Do you have your doors or windows open with screens on them? You could have a mosquito or two in your home. Every once in a while I get bitten by a mosquito that got in my home and under the covers in my bed as I have a screen door and there is a gap at the top where they obviously came in. I don't have bedbugs but do have mosquitos to deal with.