You might consider a tune up, plugs, valve adjust and oil change: try flushing your liver and kidneys and adding a few things to your diet.
Drink a glass of fresh water first thing with the juice of half an organic lemon, again at lunch and again before dinner. Get some kidney and liver cleanse tea and drink 3 cups a day. Stay hydrated.
Vitamins I feel result in very expensive urine, there are a few minerals that help with energy and digestion we no longer get from the foods we eat: Magnesium, Potassium, Selenium and vitamin D3. Study up and go slowly especially with the Mag as you can get the runs otherwise. They all work together to up your energy and stamina, Calcium boosts the effectiveness of the Mag.
Try to buy organic and avoid junk food and sodas (duh). That your Dr suggested fatty meats and fewer veggies is proof that major medical is clueless about diet. A blood test you can pay for yourself will tell you what you lack and what you may have too much of in your system; I have found this site to be invaluable as well as the free magazine each month they send if you order from them-no affiliation on my part.
WWW.lifeextension.com
If you go for the blood test make sure to have your thyroid markers tested; it acts as a governor for hormones and many of us 60+ yr olds have piled so much krap into our systems it is normally out of whack.
I would agree with the above posts that testosterone injections/supplements are not a great idea. You would still need a blood test to see what your levels are and Drs do not check the more relevant markers like thyroid and mineral levels.
Start slow, after visiting the site for the first time you may feel inclined to buy all sorts of things you probably will not need once you get the kidneys and liver flushed. Google Andeas Morritz liver flush, not easy but a rapid improvement immediately in your overall well being.
Lastly, remember nothing good happens overnight, give it all 90 days and you will be feeling much much better.
Hope this helps,