Suprise suprise CMS

Ok, I'll try to keep this brief...

I have a son who is 14, I was paying his mother monthly for 5 years directly. Then she got engaged and decided to be (I will leave this blank) and went through csa 6 yrs ago, during the 6 yrs, I've been made redundant, went onto universal credit and took a couple of "need work now" jobs that lasted a couple of months until something better came up, that job ran out of funding so redundant again, back to "need work now" job and am now working in an area I love but salary is not great. Needless to say my salary fluctuated over the 6 yrs and due to job changes and setting cms up a few times they fined me for missed payments, even when I went 3 months on zero salary this has led them to take payment directly from my employer, no issue with that, saves me the hassle of dealing with them to be honest.

Anyway, I had a daughter with a new partner, she was born in 2018, I registered her with cms the same year. I noticed in january after only getting 2 and 1/2 weeks pay over xmas 2023 due to holiday shut down and lack of children at the nursery, that cms took over a third of my salary. I called them to chase this up and also asked to check the children on my file. My daughter was never added to my case, in fact they cancelled the update the day after I initially called in 2018 and could offer no explanation as to why. I did not get am outcome, was just told to call back. 

Long story short, they have overcharged me over the 6 years by approx 3k, have added fines equating to 1.8k but have not reduced any payments and are continuing to overcharge me. This over the last 6 years has caused arguments between my partner and me, nearly had to move as we couldn't afford the rent due to the amount of cash taken off me by the cms and led to me having to take a loan out to cover it. In short this has caused so much undue stress,  financial issues and realistically has led to my daughter missing out on things because I simply have not been able to afford them. But still, 7 weeks after I spoke to them, they have not adjusted my pay rate, sent me notification 6 days ago that they will continue to charge me what equates to 22% of my salary for the next 12 months and have not added my daughter to my case yet. It just says, in progress with a date in the past as to the estimated date of completion. 

I am getting nowhere with this but I believe they have added charges consistently which are due to me changing jobs so it's took a little while to process the new info, so I believe they should be wiped, have over charged me by 3k which I need back and not by reduced payments and taking into account my daughter not even been viewed as existing that I am owed even more once she IS finally added to my case, somewhere in the region of 4.5k but I also believe that I should be due some compensation due the financial constraints they have put me under which has weighed heavily on myself and my family and had a real impact upon my mental health which led to a serious bout of depression around 4 years ago which truth be told, I am still in the grip of. 

If anyone can give any advice as to where to go before I get my MP involved so I am able  to present my case to the ombudsman it will be greatly appreciated.