Bloating, water weight, week before that time of the month question.

I have noticed over the last few months the week before I get my period I get really bloated. Yesterday or maybe the day before I noticed literally over night it looks like I've gained weight. I know I'm due for my period in about a week or so. I've just attributed it to that. I made the idiotic mistake of stepping on the scale and its 20lbs heavier than where I was. Now I know I've had a so so few days but I'm curious how many calories one would have to consume to gain 20lbs in say a weeks time not taking into consideration exercise since I hurt my back pretty bad last week and haven't been able to formally exercise. I got a little freaked out today because I ate at around 540 (half a multi grain sandwich thin, about 3 tbsp of crab meat salad, couple slices of tomato and a leaf of romaine lettuce) and was hungry again around 2 hours later and I felt both times after I ate that I was still hungry and could keep eating however I didn't because any other day I would be quite full and content eating that. I think it's head hunger so I've just been ignoring it. Any advice or response would be appreciated. I know I didn't gain 20lbs in less than a week. Just a little blah right now. Thanks.

Check the batteries in your scale.   20 pounds even for tom is a little much.  Do your hand or feet feel swollen?  If it sticks around and the batteries are fine then give your DR a call to see why you are retaining that much water.  I seriously doubt it is possible for you to have gain that much weight in one week.

I agree with the above and will add that I gain EXACTLY 5 lbs a month the week prior to my period and then lose it 5-6 days later. 20 does seem like a scale or water issue.

I usually go up about 4-7 lbs. and it all disappears right after my period. 20 seems like a lot. I would check your scale.