Hi NyLyme, welcome to the board!
I am sorry you are so sick. It sounds like you have not received agressive enough treatment and you have not been treated long enough. The doses you have taken are not in the range for Lyme disease.
You may know this already, but there are some important tips about taking Doxy. Do not have any dairy, magnesium, or iron products within two hours of taking it or it will not be absorbed properly. If it makes you nauseous, eat something substantial and non-dairy before taking it. Avoid the sun. You can get a severe burn in minutes even when wearing sunblock. Some people get burned knuckles from the sun coming into the car when they are driving, so I advise you to be extremely careful. Do not lay down for at least an hour after taking it, or you can ulcerate your esophagus. This is very painful. Drink a full glass of water when you take it for the same reason. Whenever you take antibiotics, make sure you take high-quality acidophilus at least two hours apart from the meds. This helps to replace the good bacteria and prevent yeast overgrowth. The best kind to get are refrigerated and have a high culture count. Most health food stores have them.
Are you aware of the Jarisch-Herxheimer Reaction (herx)? Often when people who have Lyme take antibiotics, their symptoms get worse or they get new ones. When the antibiotics kill the bacteria, toxins are released making them feel worse. It can be scary when it happens, but it is a sign the antibiotics are working. This is probably why you feel worse. During treatment, it is important to document your symptoms daily. One way to do this is to list the main symptoms you have with a numerical rating of their severity from 1-10. Over time when you review this, you can see when your herxes occur and how you are responding to the meds.
It is also important to learn as much as possible. I recommend reading Dr. Joseph Burrascano's 2008 Diagnostic Hints and Treatment Guidelines For Lyme and Other Tick Borne Illnesses at http://www.ilads.org/lyme_disease/B_guidelines_12_17_08.pdf He is one of the top Lyme doctors in the country, and many Lyme doctors follow his protocols. He discusses antibiotics and doses starting on page 18. I also recommend the books "Everything You Need To Know about Lyme Disease Second Edition" by Karen Vanderhoof-Forschner and "The Lyme Disease Solution" by Kenneth B. Singleton M.D.
Hang in there okay? Good help is available, and you are not alone.