It sounds like you may have Blossom Wilt or Brown Rot on your cherry tree. This causes the flowers and fruit to wither and die. Leaves may also shrivel and there may be die-back of the shoots.
Prune out any infected branches/blossoms and put the clippings in with normal household waste (don’t compost or recycle them). Pruning improves air circulation around the branches.
Spray your cherry tree with a systemic fungicide such as Westland Plant Rescue Fungus Control (containing Difenoconazole). Start applying it as the flowers open next year, following the instructions on the label.