Bedroom allowance for housing benefit

Hello there. I live in a 3 bedrooms house with my husband and 2 children (11 and 8). We receive housing benefit almost up to the 3 bedroom allowance for our area (this does not actually cover the cost of our private rent) I am just wondering if anyone knew the situation with bedroom allowance, as due to medical reasons, my husband and i do not share a bedroom so we have converted a downstairs room to a bedroom. We are in receipt of PIP. I've been informed that we should be entitled to the 4 bed rate for housing benefit if we can not share a room for medical reasons. Anyone know of that is the actually case?.
I don't want to ring the council and upset my claim if this is not the case.
Thank you