Often when i bend down to do work, i.e gardening, and am squatting or on knees, when i stand back up i feel sort of like blacking out. is that normal?

Common: That is not an uncommon occurrence especially if you stand up too quickly which doesn't give your circulation enough time to reach your brain. You may check for a drop in blood pressure from a sitting to standing position as a cause. Unless this is a pronounced drop, all you must do is to rise up slowly. If your blood pressure drops severely on standing up, see your MD for evaluation and advice.