Why can’t my son sleep like a normal baby?

My son is 6 1/2 months old and STILL wakes up every 2 hours... he’ll be asleep then start moving and wake himself up. It never fails. What do I do because I know this is not normal. His doctor told me he’s old enough to be sleeping through the night yet he doesn’t. Please help I’m basically a single mother and I’m so tired . My son never lets me sleep.