The last month or so I have started getting a leg cramp- charlie horse only in the left leg pretty much just when orgasm I'm a 25yr. Female

Muscle injury. When you orgasm, the muscles tense up. It is likely that this aggravates a small muscle injury which may be due to a tear, fatigue, or overuse of a portion of the muscle. I would recommend a gentle prolonged stretch of the muscle prior to sex in the future, drink plenty of liquids, and replenish any electrolytes with a sport drink.