how to reduce heat in circuit

how can i reduce the amount of heat my transformer is dissipating.
two transistors control the transformer,one on one off i.e. switching current,
but the transformer heats too much.
any ideas.

1. reduce the switching activity of the transistors.
2. use a better transformer
3. Use a heat sink.
4. Increase the are of your system.

what is the type of transformer?
what is the switching frequency?
are the turn/volt ratio correct?

would the switchig frequency have to be totally uniform.
could a slight time delay in switchig cause the rapid increase in Temperature

Did you design the transformer? Transformer design is something of an art. You need to pick the correct core size, wire type, and winding geometry. Are you familiar with calculating core losses and copper losses? If not, search for a good power magnetics design book, or maybe software.