The way I do the UI is by setting a fixed resolution and this will hold everything in place.
Try this:
Go to your canvas and in the Inspector go to the canvas scaler. Then in UI scale mode select Scale with screen size and set a resolution that you want for your UI. I usually use 720p (1280 x 720).
Then set Math to 0.5
Now everytime you create something in the canvas you will go to the rect transform in the inspector and set a anchor preset at the neares position where your sprite is.
For example if you are creating a Health bar in the upper left corner then select the upper left corner.