I am 5'1 and 131 pounds...and my weight loss has officially slowed down as well. It was right at 132...which for us, puts us at a healthy BMI. The unfortunate fact is, our bodies may think they are absolutely fine now.
One thing I would double check is that you are getting ENOUGH calories. I burn 1000 calories a week, and SP has put me at 1250-1630 calories a day. That's a bit more than the 1200-1550 you're at. Be sure to account for all your calories burned, to make sure you aren't freaking out your metabolism. Sometimes you have to eat more to lose weight, as strange as that sounds.