Kwesi,
I'd like to welcome you to the forum, too.
My index finger also gets a bump if I fire a lot of rounds. My fingers are long and thin, and I suspect it's the shape of the trigger that gets to me. Most pistols do that to me, so I live with it.
Before updating my R9S with the new mag springs I had a number of double feeds. They're hard to clear on any gun which doesn't have a slide lock, but I found a simple way to do it. Here's what I found works best on the double feed you described:
1. Keep the muzzle pointed in a safe direction.
2. Take a piece of wooden chopstick (or Hedley "Stop Stick") and push down on the rim of the top round in the magazine. (If you press down further forward on the top round in the mag, you may dent it.)
3. The slide will then be able to move into battery, chambering the round that was stuck.
Pull the stick out the gun.
4. Fire gun. Actually, I usually drop the magazine, examine the top round for damage, eject the chambered round & check it for damage. Then I reinstall the mag, rack the slide, and continue.