Don’t judge weight changes. Judge shape and size changes.
5 pounds of muscle takes up about as much space as 3 tangerines.
5 pounds of fat takes up about as much space as 3 grapefruit.
The most common mistake I see is then people plant their foot WAY in front of their bodies and come down on their heels. Your foot should make contact directly beneath your center of gravity or maybe slightly in front of it, with most of the impact happening mid-foot.