sos pls i need help! backdated sdp now on uc

hhello I'm new & I'm in need of some advice if anyone knows I'dappreciateany help or advice etc ....so I was on job seekers but was getting the top ups but even though i started to recieve pip enhanced daily living fr9m 2014 i never got the sdp until 2023 i was then moved to uc & given the transitional protection payment aswell as lcwra but they kept giving me what i believed was the wrong amount (less than what i was entitled to) they looked into my claim & said yes they underpaid me but i still didnt feel it was right so asked again they then agreed paid sone more but i still felt it wasnt right 20months later they randomly contacted me via my journal & told me theyd been underpaid me in april 2025 & I recieved what i was owed from when my uc started but what i have a problem with is why didnt i get my sdp from when my pip started? and can i apply for it now? i was on esa when my pip started 2014 then i went onto jsa 2017 but got 2 out of 3 top ups then 2023 they started paying me sdp but only backdated it a few months when i moved address but I'd lived at that adress years before & they never gave it to me then? i dont know why? I kbow ishould have been entitled to it can i appy now? how ? please if anyone knows i feel so ignored & messed around by the dwp ity exhausting x