Why am i like this?

I have been feeling suicidal alot lately since giving birth 6 months ago... if i encounter any type of problems, esp pertaining to marital and house, it will trigger me to have a complete meltdown.. i would want to hurt myself but my husband will stop me.. sometimes in my mind, i have this thoughts where i can scream and destroy everything and just bang my head onto the wall.. i dont know how to explain but i feel like maybe if that were to happen, it might be good. I am not even sure if i am a good wife or mother or daughter to begin with. Sometimes, when i open the window, i feel like climbing up and jump down. But when i look at my baby, i feel very guilty. I feel like i am an irresponsible & selfish to do that. I am scared.