32 wks pregnant, so tired can barely stand?

I get enough sleep, my husband is helping out a lot with housework so I'm not over doing it. I was cooking dinner and I had to sit down it was too much to even make dinner. I get out of breathe all the time. I have not put on any weight during this preg. So I am not obese. I have a different kind of fatigue than just being tired it's almost like the baby has drained everything out of me. This is my 4 th and it has never happened prior to this preg. Is it just me or a sign of something wrong?