Hi, there! The fact that you took Tylenol frequently does not definitely mean you have liver damage. It's possible you may have done some minor damage, but it's doubtful you caused severe damage.
Herbs that cleanse the liver and help it heal itself include Milk Thistle, Dandelion Root, Red Clover, and Turmeric. You can either buy capsules of the herbs, or can find teas that have a combination of the herbs. Use caution with Turmeric, as it can upset your stomach. Instead of taking capsules, try adding it to eggs, casseroles and other dishes. Milk Thistle, Dandelion Root & Red Clover are considered "tonics" that will cleanse the blood and the liver and will generally strengthen the body. If using herbal capsules, double the dosage indicated on the bottle for 2-3 weeks and then reduce it to the normal dose indicated in the instructions.
Lecithin is also excellent for healing and regenerating the liver. Lecithin can be purchased as capsules or in granules. Personally, I think the capsules are much easier to use. Take 1200-3600 mg three times per day. ON an interesting side note, Lecithin can also be used to help heal the liver from damage caused by alcohol.
You CAN reverse liver damage. I had extremely elevated liver enzymes for over 15 years. After 6 months of taking the supplements I mentioned above and making some healthier eating choices, my liver enzymes are now below normal -- which is fantastic. My doctor is amazed. Good luck to you!