weight question

I have lost over 70 pounds. I run twice a day for 30 min each and lift weights. Burning around 800 calories a day. I used to weight 240 pounds and not I weight 178. It depends though some days I wake up at 178 and others like 179.6 or even some at 177.7. It is different. I have no idea if I gained weight or not. I mean my pants still fit the same. I just am so bust through out the day I never eat a large meal just small snacks. At night though around nine o'clock I eat all most all my calories. I eat only about 1800 to 1900 calories a day. Sometimes I eat around 1200 calories in one sitting. It really hasn't affected me. I eat a lot of vitamins and such. Just sometimes I wake up three or four times during the night so thirsty. It is depressing, I worked so hard to lose the weight I just want to maintain where I am at. Is it just that I over ate at night which constitutes my weight changing in the morning plus all the water drank during the night?