just not feeling good

I'm 22 weeks and 3 days with my first baby. I am tired and feel very weak. Has anyone else had this? my husband says it is just pregnancy but I feel like it is more. I don't think I should feel as tired and as worn out as I have been. I told the nurse at my last visit but she didn't seem worried. they are going to check my blood next visit on February 20th. I am still not able to eat good and feel nauseous all the time. I've actually have lost 20 pounds since I've gotten pregnant. I am not trying to lose the weight either.