It's probably water/food weight...i doubt you gained 4lbs in fat since sunday. Might also be new muscule..?
Oh, btw are you sure the scale your using is consistent? IMHO consistentcy is more important than 100% accuracy. I have to scales that I use both read diffirent numbers but are both consistent on the numbers. The scale at my house is 2lbs lower than the one at my work ALWAYS I use both and kind of average the weights and land in the middle. My doctors scale is closest to the home one so I know that it's close to 100% accurate.
It takes 3500 extra calories to put on one pound. So unless you have super-human eating abilities, I doubt you really consumed 14,000 extra calories since Sunday. So, no worries- sweat, drink tons of water, the 4 lbs will go away .
I give water/waste weight a good 5 lbs. dont stress. Maybe try a "cleansing" to help clear out some. I use castrol oil like once a month and it makes me feel great afterwards.
Oh yea definitly water weight, just watch your salt for a couple days and drink alot of water and it will come right off (yes, drinking more water to get rid of water weight lol)
I have a WW scale that has body fat and body water included in overall weight. You could get one of these.
Don't worry about water! Just keep at it. Just giving yourself undue stress~
Those 4 lbs are definitely water weight unless you've consumed an excess of 14,000 calories. Water weight is definitely depressing though, especially when it's several pounds of water weight and it lingers for weeks.