No hot water

Baxi combi boiler 105e. 2 yrs old. Worked great for the 1st 18 months but now hot water is useless. Can only run hot taps at very low flow to get hot water. Boiler keeps cutting in and out on its own. DHW temp sensor changed so suspect heat exchanger. Also, pressure on guage keeps rising, I\\\'m always bleeding system. Could it be there\\\'s a leak within heat exchanger and pressure rising through mains pressure? Any help greatly received. Thanks.

COuld be that the system was left with flux in it. Corrosion causes gassing which you have to bleed off, and debris which blocks your heat exchanger giving poor HW performance..

Thanks Chris, I've had the heat exchanger out twice and tried de-scaling and it was slightly better for a while.