If you have severe pain in lower back, spotting between periods and earlier had heavy periods, then endometriosis should be ruled out. Another possibility is a fibroid in the uterus. Low back ache can also be due to pelvic inflammatory disease. So, an ultrasound scan would be helpful in diagnosing the problem.
If you have heartburn then you can take some antacid gel and see if it helps. Along with it you can take drugs like omeprzaole or ranitidine. Eat small and frequent meals. Avoid oily and spicy food, fuzzy drinks and alcohol and smoking.
Arm pain can be due to pinched nerves. It can also be a referred pain from chest, so get a 12 lead EKG. Another possibility is Scalene Myofascial Pain Syndrome. When scalene muscle is the cause of pain, the pain is referred from neck to to (either all or a combination of) chest, inner lining of scapula (shoulder bone), shoulder, posterior and lateral sides of the arm right up to the thumb and index finger. Treatment is by physiotherapy that involves indentifying the trigger points, and massaging them, and other exercises to relieve the muscle tension. Other than this it can be inflammation of veins or phlebitis, inflammation of lymph channels or lymphangitis, deep vein thrombosis or compartment syndrome.
So, your problems could be related or they maybe unrelated. Please discuss with your doctor. Take care!
The medical advice given should not be considered a substitute for medical care provided by a doctor who can examine you. The advice may not be completely correct for you as the doctor cannot examine you and does not know your complete medical history. Hence this reply to your post should only be considered as a guiding line and you must consult your doctor at the earliest for your medical problem.