Ecm fuse 1990 pontiac sunbird

I was driving my car about 55 mph when my ecm fuse blew out i put in another fuse the car started then the fuse blew again

The fuse may supply power to some other things also. I suggest you disconnect the connections going to the ECU and then see if the fuse blows when you turn the key to RUN. If the fuse doesn’t blow then the short is inside the ECU. If it still blows out then you will need to get a service manual and check how the wiring is designed to find out what else the fuse supplies power to.