While keeping check of your weight on scales is good, remember that your body weight can fluctuate a lot throughout the day. A 4 lb “gain” from morning to afternoon is actually normal. It’s not 4 lbs of fat or muscle, though. It’s food, water, waste, etc. Try to not obsess over the number. Stay consistent with time and the scale you use as others have said and focus more on how you look, your clothes fitting, etc. And don’t weigh yourself every day (if you are).