Depression

Ive had depression and anxiety since a young age im now 31 pregnant with my first baby and all ive ever wanted was to be a mummy. In august when i found out i was pregnant i stopped my anti depressents..ive been struggling ever since and my depression is now back i feel like ive let every one down i feel useless and that i have no right to feel like this i decided on tuesday after talking to a doctor that i should start taking them again but im scared how long this is going to last and how bad it will get. The doctor said its not risky to the baby to take them but i just feel like im a failure :( im taking it out on my fiance which is not fair because hes been nothing but supportive i dont know what to do.