Personally I never have any problems loading them to capacity. I do have to tap them to seat it in the gun though, unless you load with an open slide, still have to if you carry one in the chamber with a full magazine.
I was going to suggest maybe try a different technique to loadlike pushing down on the round on top of the mag with your nondominant thumb, and using your dominant thumb to push the next round on top, down, and back. It takes a little pressure off when using this technique. Maybe thats what youre doing? Maybe its a hand strength issue (which is fine). Some people prefer using a loader tool.
Try a loader if you have trouble that will assist you loading them. Upula is one popular brand. Try it?