To ask you to share about postnatal anxiety?

Since becoming a new mum I have had pretty bad postnatal anxiety. I constantly worry about big and small things, mostly concerning the safety and well-being of my DD. Some of the thoughts are irrational and I recognise this but it doesn't stop the feelings of anxiety and worry.
Eg. I am scared she will be abducted, what if I die? What if we have a car crash? If we do, where is best to have her in the car? What if I drop her down the stairs? What if she chokes while I wean her? Etc etc etc.
I have seen a mental health worker from the NHS who is very nice but hasn't given me much to work with. I should also say, I function through the day and we have a very active life, this doesn't stop me loving every tiny minute with her. I just have nights where I feel like I can't breathe thinking it all over.
Am I alone in this? Does anyone have similar thoughts and feelings? Any advice on coping with it?