Im so confused!

Well I'm no expert, but I would say you should be eating your bmr as a minimum, because that is what your body needs to function effectively. My goal according to MFP is 1200 ( this is based on wanting to lose 0.5 lb a week), and my BMR is 1160. So, regardless of exercise I always eat that. After that I try and eat back some of my exercise cals. You have seen my diary and I'm more like 1400/ 1500 most days.. And have still been losing.

But, if you are having results doing it following the MFP macros. Then I can see you would be worried about increasing your intake. Maybe see if the loss begins to pateau, and then maybe bump them up?

So I'm dead serious about this weight loss, MFP has put me on a 1500 calorie a day limit, I work out 5 times a week, 20-30 minutes per day, buring 350-450 calories. I usually try to eat back most of burned off calories.

I have been hearing a lot about this BMR number, which according to MFP, mine is 1593. So am I not supposed to go under that number per day? because now I'm netting anywhere from 800-1400 depending on the day.

I have lost 3 lbs in 2 weeks doing it this way but I'm afraid I'm doing something wrong? not eating enough calories? I'm just confused now

You'll luck out. Your true BMR potential is less than the estimate, because the formula's are based on studies of people at goal weight already, and certain ratio of fat/LBM. Since for weight loss people usually have more fat, the estimate is high.
With only 93 difference, just confirm eating back those exercise cal's to net at that 1500 every day.

Normally a big undercut to BMR would still experience a loss, but a diminishing loss rate as metabolism slowed. I doubt you'll see that, because you wisely selected 1 lb week weight loss goal.

Keep that knowledge in mind though, because as you get closer to goal weight, MFP will have been lowering your goal through the loss, and at some point 1lb weekly will be too much, and you'll need to adjust to 1/2 lb weekly, to keep the goal at/above BMR.

I have a heart rate monitor coming in the mail. I have been doing Jillian Michaels "Ripped in 30" and Im basing the calories off my pedometer then increasing that amount slightly to make up from the sedetary moves, plus what I have googled, reading what other people my size/height have burned doing the same work out. Its probably not 100% accurate, which is why I have invested in a HR monitor.

Sounds good, I was surprised to see after I used the HRM that I was not burning anywhere near the amount of calories my exercises calculated through MFP. So in actuality I've PROBABLY have been going OVER my caloric goal the past two weeks, and I would eat not so healthy things or more to make up for the negative calories working out gave me (still have lost 4 pounds though, but I guess that's because I've been doing some exercising). Hopefully for you it will match up accordingly. But for me it was not the case.