I injured my back weight-lifting four days ago. I've had pain, minor spasms, and loss of appetite. Advil (ibuprofen) was giving me heartburn. What shoul I do?

See your doctor. Advil (ibuprofen) can irritate the stomach, leading to gastritis and peptic ulcer disease. Heartburn symptoms should be a warning to stop the advil and to seek the help of your family doctor or internist. Additionally, he or she can also evaluate you for the back symptoms, making sure it is not a more serious issue.
See MD, Stop Advil (ibuprofen) Sounds like you have already done enough watching and waiting. Go to your physician for an examination to check for disc injury and other problems. Over the counter analgesics, physical therapy, massage therapy, yoga and acupuncture may help. Initiall cold, then warm compresses after a day or two. If not resolving, i send my patients for x-ray, mri, and referral to ortho and/or pain clinic.