Bosch combi 28i junior no hot water/heating going off?

My Worcester Bosch Combi Boiler, 28i Junior, red light flashing. It comes on after about 5 mins of me having turned on the heating and flashes slow for eg, the red light flashes in rhythm every 1/2 seconds so then I turn the boiler off.
After 5 - 10 minutes I turn the boiler back on and turn on my hot tap to run my hot water. On the boiler the red light flashes fast, constant after about 2 minutes. It has done this repeatedly for the past few days.

I cannot afford to pay an engineer right now.. Please I'd appreciate anyone's advice.
: )