I'm a diabetic type 2 and I have arthritis in my lower back what meds should I be taking for my lower back I also have CAD?

Depends. Tylenol (acetaminophen) is by far the cheapest and least harmful option. Nsaids (ibuprofen/naproxen) may be an option, but are not preferred in people after acute myocardial infarction, already having cad, like you, stomach ulcers, kidney problems, high blood pressure and leg swelling. Muscle relaxors may be ok. Even narcotics are preferred to nsaids in some cases. Physical therapy/topical rubs are an option.
Tylenol (acetaminophen) in order of preference - tylenol (acetaminophen) up to one gram 2-4 times a day(let your MD know); then consider ultram or mild narcotic; use ibuprofen rarely on bad days - makes your BP high, increases ulcer risk, increases risk of MI, makes aspirin less effective, can injure your kidneys - routine use of NSAIDS can be dangerous.
What type lower bac. What type of arthritis do you have in your lower back? There can be many reasons for people to have back pain. Your evaluation will define the type you have to try to develop your best therapy. T2dm and CAD will also influence what you can take. Medication can be helpful but exercise and weight loss are important, posture evaluation also helps.