My understanding is that to work out precisely what you're burning, you need a team of specialists and some very expensive machinery. I don't know why you're worrying about it, there are other ways to factor exercise into weight loss (BMR plus Harris Benedict formula, for example, as a guide to your calorie allowance, bumps up your calories depending on how much exercise you do- this is an estimate too, but you can find that on Google and it's a pretty good guide for most purposes)
I also don't think "should" comes into it. Are you working reasonably hard (pushing yourself but not making yourself feel sick or dizzy, nor injuring yourself), doing something that you can sustain (whether you enjoy it or simply don't hate it) and fitting it in with your other commitments? If so, you're doing well. If not, you need to rethink.
Edit to add: none of this will work if you don't think about diet. For example, if you need to eat 2500 calories a day to maintain your weight at your activity level (as unfortunately it all comes down to this), and you eat 2000, you'll lose; if you eat 3000, you'll gain. Where exercise changes this is if you need to eat 2500 calories working out 5 days a week, you may only need 2000 if you don't work out. A lot of people think they can eat more if they exercise- while this is true, it's only true compared to your calorie allowance- if you're gaining weight, start exercising, and then eat even more, chances are you'll still put on weight.