Calories and TDEE... I am a little confused

Ok so I have read on here a ton of times that the BMR MFP gives you isnt enough calories for you to eat. Which I think I agree.. haha I have been doing Insanity and am on day 4 and today I am struggling because I cannot get full. I just had lunch and am still humgry and in an hour I will be starving! I am willing to try the eat more lose weight thing I just have no idea on how to figure out how much I really need to eat!

Thanks for your help!