Oh Sally2, big hugs! I'm so sorry you're feeling so overwhelmed. Well done for making the appointment to see the GP, opening up to your partner & talking to friends. I hope by sharing your concerns taking that first step you're able to feel more in control. Being a SAHM is hard, if it's not what you had wanted for yourself then it's bound to build resentment - add possible PND & it's no wonder you're feeling like everything is too much. You're not alone, a lot of mums are great parents once they have balance & are happy.
Good luck with the GP, I hope you feel better within yourself soon.