Weird symptoms... any advice?

So for the past few months [since about Halloween], I've had chronic flu-like symptoms that I can never quite shake. Over Christmas I got really sick, vomiting and such, which prompted me to go to the ER, where they basically listened to me breathe and diagnosed me with bronchitis. So I've been on anti-biotics for the past two weeks, which made me feel a bit better for a while [although even while on them, I still had a fever], but within a day of finishing a bottle of doxycycline, I was sick again. I have a sore throat, am extremely weak and tired, and can't seem to focus, and the lymph node under my arm has been swollen for a while now. I can't figure out what the hell is wrong with me that I've had these symptoms for months and even the anti-biotic was ineffective. From everything I've read on the Internet, my symptoms seem to line up eerily well with leukemia, but I kind of doubt that's it. Any advice/comments? By the way, I'm 17 years old, if that helps.