I have a feeling of constant cramp in my foot. what could be causing this?

Sounds like: Magnesium, calcium or both deficient.

Muscle spasm: If the muscle is tight and it is painful it is probably a muscle spasm. Soaking in epsom salts might help or using magnesium oil topically, as well as massage to knead away the contraction. Check vit d which might be low. Eat a healthy diet. Excess carbs can be problem. Avoid alcohol, tobacco, sleep well, move through the day, and de-stress. Read kelly mcgonigal's book for behavioral change.

Cramping Arch: Constant vs. Intermittent is the key. Constant cramping can be electrolyte imbalance, circulation issue, nerve problem. Intermittent cramping can be mechanical (the way your foot hits the ground), shoes you wear, or circulation. If the cramp occurs when active vs. At rest it is mechanical. If you have rest pain, get to a physician.