Will I be backdated work capability?

Hi, I’m pretty new on here. But had a few questions and concerns. 

I first started universal credit in March 2018 but was previously on job seekers allowance. I was transferred over to universal credit in march 2018. I had a first interview at the job centre for universal credit and explained my issues and disabilities and health conditions, also said that I was caring for my mother at the same time. They told me that I don’t need to provide any fit notes anymore (because I previously was when I was on job seekers) and that I don’t need to attend any appointments and to let them know if anything changes in the future.

I recently found out that I needed to do a work capability assessment and that this whole time I could have been entitled to limited capability for work and work related activities but I did not know this and did not know what I was eligible for and believe my initial interview for universal credit should put me into an WCA so I could have been getting this payment since March 2018 which I haven’t been. But anyhow.. I recently got confirmation and been put into limited capability for work and work related activities but they have not awarded me since I started universal credit and have explained that it starts from when I have in my first sick note. I handed my sick note before doing the assessment as that’s what was told on my journal to report a change and then I’d go through that process ( again.. which i wasn’t aware that I had to do in order to get assessed). Which I did and have a sick note which I dated from 2017 when my first operation was and I was on job seekers at the time and having in sick notes regularly at the job centre while being on job seekers before being transferred over to UC. So yeah I’ve had an operation every heat since 2017 and condition is getting worse and worse, after being transferred over to UC I wasn’t told to hand in anymore sick notes etc like I used to on job seekers allowance. So yeah sorry about the long story but the question is, would they still backdate me from March 2018 when I started UC as i wasn’t aware that I needed to be assessed and no one told me at my first initial interview at the job centre? I also have all my medical evidence and hospital evidence for all my operations and monthly treatments that I attend. Would they backdate me to when I first started UC as it would be their mistake to not ask me for any sick notes or make me aware that I need to do an assessment or anything? I was just told that I don’t need to look for work so I haven’t been and was told I don’t need to hand In sick notes. But recently have found out that this whole time I could’ve been eligible for limited capability for work and work related activity monthly payments which I haven’t been getting.

I hope all this makes sense and thank you so much for reading.

Apologies I may have not been clear at some points.

Just to confirm, I have requested a mandatory reconsideration 2 months ago and provided all medical and hospital evidence since my first operation. I am still waiting for a decision from DWP and they just tell me that there is no time frame and that they’ll just update on the journal. 

Thank you.