Exercise

Ive been reading where it takes 21 days to form a habit.
I guess that would include both good and bad habits. Mine that I am attempting to form is of course the exercise habit. Ive done well so far. Day three lol I did do three miles today though I had to split it in twp sessions. I tried to walk around lunch time but the sun was burning my recently chemically peeled face. Not good. S0 I did one then after dinner did two more. Score! Felt accomplished. Now 18 more days of some sort of physical exercise. After dinner and exercise I updated my fitness pal and it said I was 1014 calories short for food intake. Not good cause you have to eat to lose weight. Ate a protein bar and ended up only having 700 calories after taking off what was burned during exercise. Trying to figure this whole band thing out. Footnote stupid scale hasnt moved hardly at all last few weeks and is making me pissy :(