I'm 18 years old and I haven't seen a doctor since I had a pediatrician. I'm always dehydrated, have a very high (125bpm) resting heart rate sometimes, but it's normal at other times, and I occasionally feel like I can't get enough oxygen for hours on end. I haven't had any of this looked into. I have medical insurance now, and I don't know where I'm supposed to start. Can you help me?