MrsD, I'm really glad you're getting some help. You've done the hardest bit - it's out there now and you are aware of why you're feeling like you are. You won't automatically stop feeling like that, but it'll be a tiny bit easier.
Copied this from the site I posted earlier - perhaps you could show it to DH?:
ADVICE FOR CARERS
(Partner, Parents, Friends, etc.)
Don't expect the sufferer to have fears and worries that are reasonable. When you are depressed quite small things can worry or upset you greatly.
Do try to give her as much practical help as possible. Depression makes a sufferer feel extremely tired and small tasks feel like huge ones.
Don't nag. Try to keep your patience even though it may be taxed.
Don't point out shortcomings, unfinished jobs, unkempt appearance.
Don't say "Pull yourself together. You don't know how lucky you are. There are lots worse off than you."
Don't leave her alone with the baby if you feel there is the slightest possibility of her doing harm to the child or herself.
Do try to let the mother express her own true feelings of anxiety and fear, even if she repeats herself.
Do allow the mother to talk freely and express her innermost fears without showing shock or amazement.
Do show consideration and sympathy for her in her predicament. Reassure her that she will recover, repeat this reassurance as often as you can.
Do encourage her to have as much rest as possible.
Do encourage and praise when the mother makes an effort.
Do encourage her to seek professional help if she has not already done so.
Do try to get out with friends, without the children if you can, but never force the mother to do anything she doesn't feel up to doing.
To Partners - Remember she is still your wife/girlfriend, not just the mother to a child.
Don't try to cope alone. You may find the present situation exhausting and stressful. Do talk about your own feelings as much as possible and accept any offers of help.
DON'T BE DISCOURAGED
Remember
PNI is an illness and mothers who suffer from it WILL recover.