Advice - Gaining/Losing weight

First off - put away the scale. There are a hundred reasons the scale fluctuates. Water weight, bloating, muscle tears retain water to repair themselves, sodium, TOM. Ect...

I think you should take measurments and pictures and weigh once every other week. I think other then that, you're doing it right. Give yourself AT LEAST 4 weeks then reassess.

Are you eating back your cardio calories?

Since at this point, I'm trying to lose weight, should I just stop the weights workout and just stick to cardio until I get to where I want, and then start weights again?

Hi Everyone, so I'm trying to lose that famous tire around my stomach, and it would be nice for my butt and thighs to be a little smaller. I had success with MFP before when I wasn't exercising; I was eating 1200 calories a day and I lost 7 pounds. Of course, I stopped watching calories, starting drinking a little more, and poof, the weight came right back on.
Now, I've joined a gym and go pretty religiously, at least 6 days a week, but I aim for 7. I do a cycle class 3 days a week, weights on off days, and on the weekend either cardio or weights, depending on which day it is.
So, at first, I was eating still 1200 calories a day, and I was gaining weight. Very discouraging, but I found on multiple threads that I was starving myself and needed to eat more. I found that little calculator thing and now I see I should be having 1500 (work out 4 days a week) or 1700 (hard work out 6 days a week). So even though I go 6 days a week, I don't know if it's a "hard" work out, so I try to aim for the middle of 1600. I think it's a hard work out, usually within 5 minutes you can wring my clothes out, but who knows.
So I started watching my weight patterns more closely and I found a trend. I am GAINING weight on days I do cardio and LOSING weight on days I do weights??? How is that possible, it should be the other way around? I weight myself in the morning when I wake up and before I go to bed. So for example, Tuesday was my weight day, when I woke up Wednesday, I lost a pound in total and it was all done overnight. Wednesday was my cycle class, and when I woke up Thursday, I went up a pound and there was only a difference from night to morning of .2 pounds. Thursday was my weight day, I lost .8 pounds, all overnight, and when I woke up this morning, I gained it all back and the difference between last night and this morning was .1 pound.
I'm so confused! Should I be eating differently on cardio days than weight days? And how is it possible on some days I lose so much at night, and other days I barely lose anything? Obviously I'm doing something wrong, I just don't know what?
Any advice would be appreciated.
Jennifer

Thanks everyone for the great advice/comments.

My sodium might be a problem, I pretty much eat all frozen meals which even though they are weight watchers, I'm sure the sodium is threw the roof. I eat a WW breakfast sandwich in the morning, a WW or Lean Cuisine meal for lunch, and a WW dinner. Then, I'll eat a granola bar between breakfast and lunch, a small WW snack between lunch and dinner and peanuts thru out the day. Everything is within 1 serving size, so yes, I count out 38 pieces of peanuts and put them in my container! LOL I'm not perfect though and go out to dinner every now and again. But, I will usually cut my portion in half, and make sure I don't eat too much during the day because if I'm going to a nice restaurant, I'm not getting just salad with no dressing!

I was calculating my calories based on the Harris–Benedict method. I found a thread on MFP with a link to some calculator. It was basically finding my BMR (1294), then times that by the work out multiple (moderate active is 1.55, very active is 1.725, etc) and then that number by 80%. I'm using MFP to keep track of my calories, but I'm using the Harris–Benedict for the amount of calories I should be having.

Since at this point, I'm trying to lose weight, should I just stop the weights workout and just stick to cardio until I get to where I want, and then start weights again?