antenatal depression

I've been to see a therapist and she told me I'm suffering from antenatal depression I've also been having problems with my step daughter which I never had I've not been wanting to be around her or do anything with her or for her. She said I am resenting my step daughter because this is my first baby and she's stopping me from been able to rest and be a first time mum, it really worries me that I'll never be back to the way I was with her