I know someone in his twenties, who reported exactly the same thing after taking a course of Doxycycline. Although it didn't effect his libido, just gave him erectile dysfunction. If you read the book "Missing Microbes" by Martin J. Blaser, who is the Muriel G. and George W. Singer Professor of Translational Medicine, Director of the NYU Human Microbiome Program, former Chair of the Department of Medicine, and Professor of Microbiology at New York University School of Medicine. In 2013 he was elected to the American Academy of Arts and Sciences. He is an established researcher in microbiology and infectious diseases. Blaser's work has focused on Helicobacter pylori, Campylobacter species, Salmonella Bacillus anthracis, and more recently on the human microbiome.
If you read that book, then everything will make sense! And if you think microbes and missing microbes can't and don't effect/function the brain and endocrine glands, think again! Check out the work of Sarkis Mazmanian, PhD Louis & Nelly Soux Professor of Microbiology, and David Perlmutter, MD, amongst many others
Have you tried coming off the drug to see just how things go for a short time, or have tried looking up the drug to see what are the side effects of it is and does it lower you libido, and thats just for starters.
Keep your self busy for a while searching for the facts.
Good Luck