Hello there hairytale I am not a young mum but a grandmother, but I can absolutely assure you (as others have done) that the way you are describing your depression and anxiety with its ups and downs is very characteristic of the illness. I am no medic but had a major episode of depression 2 years ago and was in hospital for 3 months and since then my life is like an emotional roller coaster. In the early months after discharge I had a bout of bad days every few weeks, and this has continued although I can be fine for weeks and months now and then wham out of the blue I wake feeling flat, empty, no motivation, crying, full of negative thoughts.....no warning, no trigger, just out of the blue and can last anything between 2 and 7 days. I find the worse thing is explaining this to people as I can never really make plans, just in case it's a bad day, but real friends understand, and I'm lucky to have a supportive partner.
I have been seeing a psychologist on the NHS but she has not been able to help about this "up and down" thing. The consultant psychiatrist told me that this was very normal and these "blips" are to be expected. He said they usually blew themselves out eventually but with older people (I am 68) they sometimes don't and you have to work around them.
Can you say why you won't take ADs - these drugs are very safe and usually very effective; they were certainly a life saver for me. I see mnay MNs who are afraid of ADs as they have heard horror stories of being "zombie" like or some such, but that this is not necessarily the case.
Re the negative thoughts, these are a symptom of depresssion/anxiety (as these two almost always come together) and they can spiral downwards and you end up scaring yourself stiff. Anxiety is the medical name for fear, and when we have the negative thoughts that pop up automatically we go into a downward spiral and scare ourselves even more.
CBT does offer a way of alleviating this anxiety, though it is not always easy. It is quite a simple theory and attempts to cope with the automatic negative thoughts (ANTS) and replace them with the something more balance. My therapist asked me to write down all my negative thoughts and how awful things could get etc etc etc and then ask myself is it accurate is it helpful is there an alternative (she called this AHA).
Then she asked me to write down a more balanced account of my thoughts e.g. "That might not happen, and I may not feel so overwhelmed by these thoughts, although they might be unpleasant, and I will know it is a symptom of depression/anxiety etc etc" and then ask yourself which of the two scenarios is helpful and which one isn't.
You are only young and there are lots of young mums on here who have/had PND and there will be brighter days ahead.....
There are many books on CBT on Amazon that you could look for while you are awaiting therapy.