Can you plateau before you start to lose weight?

You're most likely not losing because you're not eating enough. Scary though, I know, but up your calories for a few weeks (give your body time to adjust so don't judge it on a couple days) and see what happens. Eat all 1200 AND part, or all, exercise calories.

I weigh about 150 lbs currently, and I'm 5'3" tall. I try to eat between 800 and 1100 calories every day (which is harder than it should be for me) and I exercise three to four times a week. But I've been doing this for a month now, and I have seen no change. I've tried switching my diet around, by eating strictly healthy meals, going no-meat, but nothing seems to be working. Is this something I'm doing wrong, or should I be seeing a doctor about why I'm not losing weight?
Thanks for any input [:

At 150 pounds, you can probably lose weight on 1400 calories effectively. At your weight, 800 calories is just far to little and it will inhibit your weight loss.
Try calorie-shifting as well. It may increase metabolism.

You're most likely not losing because you're not eating enough. Scary though, I know, but up your calories for a few weeks (give your body time to adjust so don't judge it on a couple days) and see what happens. Eat all 1200 AND part, or all, exercise calories.

I completely agree

I agree with the other posters. You are most definitely not eating enough, which is why you have hit a plateau. Your body is slowing your metabolism to conserve energy. Eat more and you should see/feel an improvement. Also, make sure the calories you are consuming are "good" calories. You should be eating a balanced diet of fruits, vegetables, whole grains, etc. Limit alcohol and unhealthy fats. Cut out processed foods and try to eat whole foods only - those are the foods on the outer perimeter of the grocery and they don't come in packages. If you still have trouble, consult your doctor or registered nutritionist.

You didn't mention any exercise or fitness. Do you do anything physical?

I've decided to eat more calories, even if it takes me longer to finish meals. And I generally walk for a couple of hours three or four times a week. I also do yoga occasionally. I'll keep everyone updated on what happens [:

Unless you have a medical reason for not getting your heart rate up more than what a walk offers then you should try to get a couple days a week with a more difficult exercise that walking. Yoga is amazing for keeping yourself stretched out and also building muscle. If you add a little more difficult exercising to your routine you will most likely find yourself considerably more hungry. That may help you get the extra calories you need to get over 1200.