What can cause internal and external pelvic pain as well as intense lower back pain?

Many causes. There are so many causes it is hard to go through them in this format If you are concerned follow up with your doctor. Consider a pelvic pain specialist pelvicpain.org Infection, Masses, Scar Tissue, Inflammation, Muscle Spasms, Nerve Disorders....
Back pain. There are many causes of back pain: arthritis, herniated disk, compression fracture, kidney stones or infection, shingles, strain among many others. Physician can help if you go for evaluation.