So many problem.. need answers. HELP!

I have felt fatigued all school year and i have no idea why. I also have never gotten a regular period and i am now 19 and have had it for 6 years now. About three weeks ago I started having terrible lower back pain, which caused nausea. I went to the ER 4 days after the pain started because the pain became unbearable and i had a rising temperature of 101. The hospital also did a pelvic exam and a UA and said my cervix was extremely inflamed and the pain during the exam was unbearable for me. They treated me for a UTI and PID with oral antibiotics and tested me for an kind of STD (which i am clear of) . After i was finished with the antibiotics i went to my primary care doctor for a follow up and she gave me muscle relaxers(for the back pain) and something to bring down the inflammation. I also got blood tests for Lymes Disease, Mono, Thyroid, Liver and all that came out regular. I am still experiencing lower back pain, fatigue, and pain with insertion of tampon and during sex. I am also still experiencing a low grade fever once in a while too. If anybody know whats up with me, or have had a similar experience I would love to hear!