pnd and abuse

i've had pnd since i was pregnant.my child is 6 months old now and it just is'nt getting much better. although some days are not as bad as others i still feel so scared that i'm going to abuse my baby.i was physically abused as a child and i'd rather die than do that to my own child. how do i make sure that i don't hurt him.? i don't kmow what to do. i spoke to a friend of mine about it and it's not something that i can realy talk to anyone about.i feel so guilty.as a single mother many people tell me i'm doing such a good job raising my child without the man that impregnanted me but i just feel that i'm the worst person in the world.