Weight gain in 5 days or less...?

i was a nice weight...140lbs...and im now 132lbs....i lost 8 lbs in less than a month...and u can really tell..like..my height is 5''5'..so i have a lil height on me...and i even lost 1 1/2 in. around my backside...its kind of dissappointing...i want to gain this back ASAP!!! and within the next 5 days if possible =]..THANKZ♥