Can exercise cause a stall?

I have started a exercise routine where i do 30 min on the treadmill and then a 30 min workout dvd that is pretty intense. I mean It is non stop and it alternates from workout circuit on Monday and Tuesday then a cardio routine on Wednesday and repeats the rest of the week with Sunday being a rest day. I have not been losing any weight and in fact have gone up and down the same 2 pounds since I started. I am 7 months post op and have been losing at least 3-4 pounds a week I thought working out would help me to lose the weight faster? should I just go back to not exercising or do I just keep at it and the weight loss will pick up again?

edited to add: my calories are 750-800 25-30 carbs 96oz of water a day 104 grams of protein a day.

I'm not sure if exercise would cause a stall. I have heard that when starting up a workout routine that the body holds onto the extra water weight till it figures out that this is the new routine & starts to let the weight go.

Stalls are going to happen whether you work out or not so you might as well keep up the exercise routine for the health benefits that your body gets, but as another poster has said, weight loss starts in the kitchen. Keep up the good work! 

Your body will just have stalls and stopping points.  But most people continue to lose for about 18 months after RNY.  The biggest loss is usually in the first six months.  You will find for most of us exercise makes us feel better but has no effect on weight loss.

Basically any time you change anything there's a chance your body might react with "OMG WHAT ARE YOU DOING" and stall.  It's a finicky jerk that way!  Once your body adjusts to the new normal, the stall will end and you'll start seeing loss again.  

Also, exercise is a very small part of weight loss, but it's really healthy for tons of other reasons.  Don't expect that it'll help you lose weight faster, but it's still important for overall health.  

Thanks for the replies, when I woke up this morning I was down 2 pounds. but yesterday I ate about 250 calories more then I usually eat because I had read that if you eat more calories then you will break the stall, now I don't know if this is true or not or just a coincidence. I really don't think I should be eating that many calories at 7 months out, it was about 1050 calories. It wasn't junk It was prunes because I needed the fiber and carbs. I was getting dizzy when I stand to the point I would black out for a few seconds and if I add some carbs the dizzyness goes away for awhile, So I try to up my carbs every few days or so. I will stick to the exercise because It makes me feel so good and I actually look forward to the next day when I can do It again. Its so weird I never thought I would be that person who loves to workout

Intense exercise that you're describing absolutely can and will stall out your weight loss.  Your weight loss, not your FAT loss.  And that's what you need to focus on - loss of fat rather than numbers on the scale.  

Hear what I'm saying:  just because the scale isn't moving doesn't mean your body isn't shedding fat like a bad habit.  It probably is.  But when you start any kind of intense exercise routine your body clings to every single ounce of water because of the inflammation your muscles are experiencing.  A gallon of water weighs 8 lbs.  

Exercise isn't about losing weight or losing weight faster.  Exercise is about strengthening neglected muscles that haven't been used in decades and increasing your cardiovascular fitness level.  Exercise is about moving with more strength and grace.  And exercise eventually will be about building muscle to replace the fat you've lost.  

The battle of the bulge is won in the kitchen - pure and simple.  You need to unhitch your  mind from the idea that exercise will "help you lose weight faster".  It will not...but it will make you stronger, healthier and more fit.  It will make you a more efficient fat burner for the future.  

And even when the scale doesn't move you should be dropping inches.  So take measurements and stay off the scale.  You're doing everything else perfectly!