Is it possible to suggest anything please to help with my long waiting submission to swp over pip?

Is it possible to suggest anything please to help with my long waiting submission  to swp over pip . I lost about 15 thousand pounds for it taking 4 years to get onto PIP from dla at same levels.  I've written last year to a minister which put me half way backdated. So I was paid for backdating 2 of the 4 lost years. Now I need to submit gp letter to prove I'd the same needs for the first 2 years of PIP. Sorry if it's not clear.  

I was 10 years on dla. Got high both indefinite. 

I 2015 had to have PIP. Applied  health professional only allowed me to get decision of standard Daily Living. 

It's quite upsetting on top of having severe health conditions,  permanent  disappointment. 

Any help. It seems dwp complaints say I'm asking fir backpsy on LEAP review grounds only.  I had LEAP letters re 3 PIP law changes not affected my awards. I think they do.