Hanna,
It does sound like you have low self esteem.
And you have also had a lot of stresses just recently what with moving and being pregnant.

I think you are being a bit hard on yourself.
You said, "If I don't do it then I get punished fo it..."
Punished by whom?

What you actually need to say to yourself is
"I'm doing the best I can."
"I'm allowed to have a rest."
"If I do this job, I will have a treat and put my feet up for an hour"
Talking to yourself in this sort of way is alot more helpful than the pressure you were putting on yourself.

Remember that you are 7 months pregnant and you can have a break, or even spend all day in your nighty if you wanted!
Pamper yourself and don't feel guilty about it.

The other suggestion would be to have a chat with your doctor or nurse, they will hopefully reasure you and maybe put you in contact with other Mums.

Good luck!