potterton proforma 28 gas boiler has high bar pressure !?

i noticed 2day that the pressure on my boiler was very low so turned it up t0 1 and half bar, to my horror it kept going up until it was 3 and a half bar,even tho i made sure valve to turn pressure was off, there is water dripping outside badly down the wall and the pressure dsnt seem to be dropping, the water heats fine and everything seems to be working great, i have tried releasing safety valve as i have dun in the past and bleeding radiators but nothing is working and outside is flooded.the boiler has been making sum loud clanging noises then stopped but pressure went back up again. I am at my wits end as i,m single mum on low income and would appreciate any advice
thankx pam

pamela f
July 2008