Help with TDEE

Please help me sort this out.

Sex: female
Age: 30
Height: 5 f 3 in
Weight: 110 lb

About 4 months ago I started exercising and went from sedentary to working out 1 hour 6 x week. I do boot camp 3 x week and run 1h 3 x week. I was nursing my 3 month old baby when I started but now I'm weaning her off. I lost my pregnancy weight and I'm down to my normal weight. I don't want to lose anymore. And I don't care if my weight goes up a little (as long as it's from muscle not from fat). I've been tracking my body fat% and it's around 21.5%. I'm very happy with my results so far and want to continue this new healthy lifestyle.

How do I figure out how many calories should I eat? At work I'm in front of a computer, but walk around a little. I put down as light activity. MFP is giving me 1600 calories to eat. For the past week only once I was able to stay within my calorie budget. It's so hard. I'm logging my exercise and adding that to my calorie allowance. Am I doing this right? I started logging about 2 weeks ago and it keeps saying I'm gonna gain weight because I overeat. Could this be wrong? Maybe I just need to eal less? Any suggestions?

In the past week I ate an average of 2180 cal per day. I burn 390 cal on boot camp (per MFP) and around 450 cal running. I don't have a heart monitor so these are based on my weight, pace, etc. Do you know a better way to figure this out?

Thanks