What am I doing wrong here?

So, it's been a week of my diet. I know, only a week, but here: Previously, when I was 20 lbs lighter, I tried to do this same thing. The difference? I ate less, but my activity level stayed the same. Though, I admit that I made a conscious effort to stand more, walk around the house more, etc. However, now, I only need to actually burn 140 more calories per day to give me a 500 calorie deficit. I am fairly sure that walking around stores for a while everyday would be enough to burn that much. I could for sure be wrong, but I just don't see how such a little amount would be hard to knock off? 

Should I change my cals, or what should I do? Maybe I think I am burning off 140 cals but I am not? It is really not a lot, but for some reason, I don't feel like I am doing everything I can to lose the weight. I feel like something needs to change. Maybe my activity level? I was thinking of joining the YMCA and using their fitness center. Would that be the best change I could make, or would changing my calorie intake to maybe 1500 be successful as well? OR, do you think I am jumping the gun here?

Find a good balance that you can see yourself living with because that will be more effective long-term than trying to rush things with excessive exercise or dramatically less food.  

A 'light' level of activity would be about half an hour a day of anything that's reasonably vigorous .... dancing, walking, cycling, gym.   It's good for your general health as well as helping you lose weight so it's not a bad habit to get into.  Then enter your stats into the CC calculator with 'light' activity and a reasonable goal date and see what comes back. 

Best of luck

Here is the thing. The first time around, when I put sedentary, CC told me to eat 1250 cals a day -- without me even setting a goal date. 1250 cals? Yeah, maybe if I was more concerned with becoming anorexic, I would do that. On other members advice, I was told to eat at my BMR, which is 1620, but I lowered to 1600 to make it even. Now, when I put in light activity, CC tells me to eat 1450.

I am not sure what to believe. I hear a whole lot of stuff about how eating below your BMR is going to bring upon hell fire and brimstone. I also hear a lot about how when it comes time to actually get past a plateau, I would need to lower my cals, and eating at say 1400 wouldn't give me much wiggle room if I had to lower them 200 cals, which would put me at 1200. 

I am honestly sure of what to do here.

Actually, lots of people find that raising their calories gets them off a plateau. Plus, there is always exercise to increase a deficit.

I'd say eat 1600, and use exercise to get your deficit up - walk a lot, join a gym, ride a bike... whatever feels right to you. There is no one right answer.

What stats are you putting in?  Height, age, weight?

5'8, 21, 180

I don't know if walking around leisurly for 30 minutes would burn 140 cals. It seems a bit high to me, but I'm no expert.

If you want to loose weight faster, cut more calories. I know it's hard to believe the BMR cals because it was confusing to me too. I'm eating around 1200 cals a day. Granted, I am only 5'2! But I have been eating a LOT more protein and because of that, I am staying full and don't need more food. I was previously eating around 1600 and going no where. So perhaps trying that would help give you a jump start. But I didn't see the weight come off for about 2 weeks so don't give up yet! I'm betting you don't need to cut back to 1200 since your taller, but 100 cals here and there will help.

Here's some ideas for lean protein: tofu chicken fish tuna beans veggie burgers and veggie products eggs protein bars for snacks

Try to incorporate protein in every meal and see if it doesn't help. Good luck!

I ran your stats and got 2000 as your burn rate at sedentary.  My suggestion is that you eat 1600 to 1700 calories and go for a 30 minute vigorous walk. You're not going to burn very many calories taking a leasurly stroll; you'll need to work up a bit of a sweat but you certainly don't have to kill yourself.  If you start out with a 30 minute walk and gradually increase your time and/or your speed, I'm pretty certain you'll get results.  Good luck!