But you're lucky, relatively speaking. If you were shot in the heart, your blood pressure would quickly drop, but it would take 10 to 15 seconds to lose brain function. In that time you could draw your gun, utter last words, or spend some time thinking about your unfortunate situation.
Caffeine can cause indigestion, which in turn may lead to heart palpitations. However, arrhythmia (abnormal heart rhythm) can also cause palpitations, and this condition is more of a concern. Seek medical attention if your palpitations last longer than two or three minutes.
In brief: Fetus/uterus growth. Heartburn and indigestion are caused by the increasing abdominal pressure, due to the enlarging uterus. Hemorrhoids are caused by increased pelvic venous pressure - same cause. Not all pregnant women become constipated, but the fetal and uterine enlargement surely can lead to GI distress. I suggest a good diet and good hydration.