I agree w/ Mandalinn, but I would also like to add something too. I'm actually like you in height & weight, so I should tell you what I do: I workout like a crazy maniac! I lift weights w/ my hubby (like a man), but I use lighter weights than him, of course. I think that's a huge important thing to do because it'll boost your metabolism. I do this at least 3 times a week. I also do lots of cardio 6 days a week and on the 7th day, I stay active by walking my dog. For instance, yesterday, I did a bootcamp class outdoors for 1.5 hours. Then, at night, I swam for 30 minutes (breast-stroke burns a lot of calories). My reward was 10 minutes in the jaccuzi.
If you suspect that you might have a thyroid condition or some other medical issue, then you should definitely go to your dr. However, most likely, you need to be patient w/ your weight loss (easier said than done, I know!) and maybe bump up the workouts.
One last thing: I suggest you journal all your foods for a week and see how many calories you're consuming. Then, check your Resting Metabolic Rate (online calculators can be find on Google) and that will tell you how many calories your body burns at rest. Then, you could eat a little more than that and experiment w/ what works. Good luck!