Tea drinking. If the tea is caffeinated, then excess caffeine can irritate the heart, possibly causing it to beat fast or skip beats.
Not many. Depends on what kind of tea, though. There are some herbal teas that can be toxic in very large amounts. Black and green teas have caffeine, and too much caffeine can cause jitteriness, keep people awake at night, produce hand tremor, and has a withdrawal syndrome consisting of severe headache and irritability. Generally, as with coffee, I recommend limiting oneself to 2-3 glasses per day, in am.
Dehydration. Tea is more dehydrating than coffee. Drink water or dilute juices also. Are you having any symptoms?
Overstimulated. Decaf still has some caffeine and 15cups is too much. Decaffeinated drinks can dehydrate you causing fatigue, palpitations, and difficulty losing weight. For every oz of decaf you still need1oz of water to hydrate your body. Stop the addiction. You will feel so much better after 1 week of serious withdrawal.