Combi boiler losing pressure rapidly and leaking from outside safety pipe?

i have a boiler and it keeps losing pressure when i topped the water up it was gone again within 2 hours and could not find any leaks anywhere so topped system up again and noticed it was dripping from the pipe that goes through the outside wall and when i fired the boiler up this drip started to increase to slow running waterand within 15-20 minutes the pressure had dropped back down again to the red section on the clock. so now i have no heating or hot water, Any ideas please??