I've had this pistol for a while and it worked fine but when I was at the range I pulled the trigger and 3 rounds went off and now it won't stay cocked unless I hold the hammer down or slide back for a few seconds so It prevents semi fire. If anyone knows what is wrong and how to fix it, that would be great.

Did you buy it new or used?

Does the trigger stay back after you pull it?

When was the last time you did a deep clean?

I bought it used but it worked the last time I went to the range, I cleaned out the trigger mechanism and still nothing and no the trigger moves normally

Couple of things might be wrong. Your firing pin might have debris in the channel and keeps it in the forward position, firing a round as the slide moves forward. I had a similar experience with an UZI and a Colt 1911. Small particles in the channel held the firing pin forward setting off the next round.

The other would be a broken sear or sear spring.  

I would remove the firing pin and clean the channel and also clean the sear and hammer area with Carb Cleaner. Relube  and try again.

I cleaned the trigger area with carb cleaner and cleaned the firing pin hole and still nothing. I thing the sear spring may not be tight enough on the sear