Hi Lisa, and welcome to the forum.
The recoil spring in these small guns is quite strong. This is necessary in a small light gun (especially the small polymer pistols).
There are alternate techniques for racking a gun that will help you through this.
You to not want one of the EZ pistols. I've examined a number of these, and had students show up to class with them. They are constructed to a lighter mechanical standard, and I've seen them fail very early in their service life. One student had new one jam on the third round shot at our range during a class.
First, if you want to replace it, consider the HK VP9SK. This polymer pistol has a bit more capacity, and a couple of small ears at the rear of the slide that help with the grip. These are expensive guns compared to your Shield.
Second, if you want to learn a better technique, start with these links:
You don't pull the slide over the frame... you hold the slide steady, and push the frame under the slide. There are stronger muscle groups available to do the second technique.
I perform the technique with my hands more extended than the instructor in the video, still pushing the frame under the more stationary slide.
Consider taking a basic pistol class from an instructor that can observe you and coach you one step at a time. It can make a great deal of difference.