How do i fix my blinking engine light on my car?

Hi, my car has been acting up lately and I have ask numberous mechanics and nobody can help me. My car has been banging and jerking (if you drive under 40) and once it bangs the cars revs and doesn't shift, this car is an automatic. The engine light was on and it said "4th gear malfuntion" and now the light is back and it just started blinking....what do I do? Please help me !