HI happy 2018 everyone

. Can anyone please give me some advice? I have rhumatiod arthritis and chrohns which is severe (wheelchair bound and bed bound most days) I was awarded DLA higher rate indefinately about 10 years ago through a tribunal. The new Pip assessment came to the conclusion to put me on a standard rate and only for 3 years when my condition has not changed.. is this legal? The pip assessor came to my home and was extremely patronising ! He told me my illness can change.. being a paramedic i feel he was not qualified to assess my disability! Any help appreciated. Thankyou