I believe the problem is that you have "If getkey(4)" twice in there.  What I do for getkey, is store it into Theta or K, after storing 0 into (Let's just Use) K, outside the loop.
So:
If K=0 : GetKey->K : End
Then, whenever you check keys, do if K=4 or whatever.  When you are done with the key to check, and the routine needs to flag the key as taken care of, you store 0 into K.

That's what I would do.  Because you have to "recognize" the key by setting K to 0 in order to do it again.  This also helps prevent the same key being pressed over and over, and the game lagging behind, while it's just pressing that key too many times or whatever.

Use a modified version of this:

http://ourl.ca/9659

Don't subtract the delay variable when checking the address, and that should result in instantaneous key replies, but only read the key once. The problem with using getKey?K is that you can only read one key at a time. This solution will also add delay so that the character doesn't have automatic machine gun fire.

Also, to shoot more than one bullet at a time, keep your bullets in a table with five variables per bullet:

• Alive/affiliation (0 for dead bullet, 1 for you, 2 for enemy, this keeps you from shooting yourself)
• X and Y position
• X and Y velocity

Then, when you shoot, store the bullet into a dead bullet slot on the table. Then, every frame, update the bullets and draw them.