Congratulations!! 13 lbs is great! 15days is a true accomplishment! I wish my headaches would disappear like that! I think you pulse racing during activity is probably normal-esp if you are not used to doing a lot of vigorous physical activity or workouts.. i'm sure with the more wt you lose the easier exercise will become and your heart won't have to work so hard to pump blood through your body.. but i wouldn't go for a run or anything like that.. only light walking with resting breaks..
i workout regularly when not fasting and my heart is noticeably trying to work harder when i am fasting. but the main thing that i have to be careful of is standing up too quickly or climbing stairs, lifting things.. sometimes i feel dizzy/weak or like i might pass out.. but i think that's pretty normal too.. because usually if people go with out food-their blood Sugar levels are low-causing dizziness..
how long are you trying to fast for this time?
today is day 2 for me! i'm terribly board right now but still thinking of food-wish those thoughts would vanish too! ha.
keep up the good work and happy fasting!