I am on my "period" on birth control pills (2nd cycle). it is heavy like it was before being on it. is it normal to have pms (cramps, back pain, etc) ?

Maybe normal: Pms can be divided into physical symptoms, like you described, and emotional symptoms (moody, anxious). The physical symptoms are directly related to the actual bleeding process, and i would even expect them with a pill "period", especially if it's heavy. Mood symptoms may be worse with a "natural" cycle. Ask your gyn to help you find a pill that makes your periods lighter, or less frequent.