Need help about pregnancy

First off, I have made an appointment with a doctor but I have to wait until December! My doctor is in high demand. I am not on birth control and I regularly have unprotected sex with my fiancé. We want to get pregnant but haven't been able to. My periods have been late the past 2 months. My most recent one only lasted 4 days instead of my normal 7-8. The past couple of days I have had severe nausea, back pain and headaches. I still have 15 days before my next period is due but I am not the patient type. Anything I could do to find out sooner and things I should do/avoid until I know that I am or am not pregnant? Thank you in advance.