Carol
The needle is not seated in the tip properly which is why when you push down on the trigger it sprays paint.
It could be a dirty needle, dirty fluid tip, bent needle or just not fully forward in the nozzle.
By dirty I mean such a small amount it might not seem to matter, a spec of dried paint.
This would keep the needle from seating in the nozzle correctly allowing paint to flow when it shouldn't.
Inspect it all very carefully, very carefully the problem is there it has to be clean to function properly.
This is very frustrating when you are new to airbrushing but once you have some time in, become comfortable using the airbrush it's really nothing to cause second a thought. You clean it, its sprays correctly you go on about your day.
Its most important to use a USER FRIENDLY airbrush paint when learning it will cut the frustration factory by 90% over using textile, craft paints. Golden airbrush colors, Comart, DR P H Martins are the paints you should be using.
this will help you I hope
airbrush trouble shooting
also check out this forum
http://airbrushtechnique.com/forums/f458/
Fontgeek or some other members hopefully will jump in and help you further
Its just paint, relax and have fun
welcome to airbrush technique