Hi I'm 15 Year Old Female And I Have Been

Hi I'm 15 year old female and i have been nauseated for 3 months now I'm know I'm not pregnant because I'm still a virgin but I have mucus that drains down my throat my mom said its post nasal drip and I havt been able to sleep because I'm so nauseated the thing is is that I havnt throw up from the post nasal drip but I'm nauseated a lot can you please help me to get rid of the nausea and post nasal drip?