Aimlessly on "Bed bug behavior?"

I'm almost positive I have bed bugs. I'm just confused about what's happening. At first I had more than one bite at a time, then I washed all of my bedding and it went down to one single bite a night. My mattress and box spring are encased from a round 2 years ago. My aunt and I looked and we saw no signs. I put down a DE powder and the bites stopped. One week later exactly the bites started up again. One bite a night. Always on my ankle/foot with the single bite. The highest up was my shin under my knee. It has happened when I was awake but I was reading or some other calm activity. I'm the only one being bitten even though my daughter fell asleep in my bed with me the other day and it's only in my bed.
Why the week without a bite? Why just one bite a night? Why doesn't anyone else get bitten even if I get bitten while they're in the bed with me?