Calorie intake/BMR confusion. Please help :)

Hi!

Just a short summary about me. About a year ago, I was finally getting to where I wanted to be (weight/health wise). I was working at a gym, standing all day and eating somewhat right. Then I got a job sitting all day and I've gained all my weight back since last year. I want to say 10 lb, but it's probably more than that.

Exercising is not a problem for me, although lately I've been slacking. I always take cardio kickboxing for an hour on Mondays, and then at a minimum, two more times a week if not more, I run (15-30 mins) @ 1% percent incline, speed anywhere from 5mph - 6mph depending on how I feel. I then weight train for 30-40 mins after my run. Usually one day is upper body and the other lower. I try to lift heavy, I'm not as strong as I want to be, but depending what exercise I'm doing and whether or not it's dumbbells or machine I'd say 17.5 lb + @ 3 sets of 10 reps.

Anyway, my main problem (unless you can point out exercise mistakes as well) is my eating. I wasn't keeping track for a while and now I'm getting overwhelmed. I'm getting overwhelmed because like a post earlier on this forum, there's confusion on how many calories to cut. MFP tells me I should not eat more than 1,200 calories a day unless I exercise and then I get extra calories. I went to FitnessRX online and it gave me a formula to calculate my BMR. My BMR is 1,445.35 and if you're sedentary you're suppose to multiply that number, and I get 1,734.42 and if I exercise 1 - 3 days per week I get almost 2,000.

What does this all mean? Am I supposed to eat lower than my original BMR or the numbers I got after multiplying based on my activity level?

I'm the type that gets overwhelmed by all of the possibilities on how to lose weight and then wind up panicking. I want to be fit for life, but I also would like to lose weight to look good by November for a trip to Mexico. I'm 5'1 and 147 lb.