I strongly urge you to consult with your Physician on this. Once you discontinue the pill or shot, you can expect to experience some adverse reaction as a result of your body adjusting to it's decrease in hormone levels.
These are considered to be mild and non-life threatening, however. They should go away on their own or until the shot wears off.
Nevertheless, the sharp pain in your arm and chest may be more severe. Getting off of the pill was your best decision.
Some women are not able to take chemical methods of birth control because or rare, serious side effects such as ACHES. ACHES is any or a conbination of:
Abdominal pain(severe)
Chest pain (severe or shortness of breath)
Headaches(severe)
Eye problems such as blurred vision or loss of vision
Severe leg pain (calf or thigh)
Hope this answers your question!