If coffee's caffeine isn't doing it for you anymore (I assume meaning wake you up) and you're concerned about your health, then adding more isn't a good idea. You need to cut out caffeine entirely and sleep more.

You can go cold turkey (I have had to do this) or you can taper yourself off to nothing over a week or two, but you've got to stop. Excess caffeine consumption does bad things to your mood and your blood pressure. Taking it to stay awake wrecks havoc on your sleep cycles and ability to get well-rested.

I know from experience that going without caffeine sucks. You'll feel tired and want to sleep--do so and go to bed early; many people drink coffee instead of sleeping properly, which isn't healthy. Drink lots of water to rehydrate yourself--if you're used to drinking lots of caffeine, you're likely used to being chronically somewhat dehydrated. It'll also help with the headaches, which are just withdrawal symptoms. (Don't take aspirin for those headaches as it is mixed with caffeine for increased efficacy. Use acetaminophen or ibuprofen instead.)

During this withdrawal period, which last only 2 weeks or so, you probably won't feel great, but then you'll start feeling better. You're basically detoxing yourself.

And then, if and when you feel like you need to get back into coffee consumption, don't have more than 1 12oz. cup of drip a day. You'll get your morning boost and the antioxidants, but not so much caffeine as to start the whole too-caffeinated-to-sleep-so-I-need-more-caffeine-to-stay-awake cycle.