My body is always hot. Why? And I am too lean and skinny. I have bulging veins on the dorsal aspect of both hands and it's looking ugly.

See your doctor. Heat intolerance, weight loss may be symptoms of overactive thyroid gland, and seeing your doctor for evaluation of this will help. The bulging veins in your hands should be left alone. As you gain some weight they should become less obvious.
Hot body. Several possibilities. You may be suffering a hormonal problem and you should discuss your situation with your doctor asap.