how do i know if i have a yeast infection?!

so before i started having SEX i always suffered small vaginal infection from the outer part. in my future when i started having sex (i have 1 year sexually active) gotten like 2 vaginal infection normal (not yeast infection just irritation) later on i took some antibiotics with out prescription and got a yeast infection. my dr gave me treatments and it went away but i don't know how come every time i get my period im always so itchy and it burns once my period is gone its still itches so i used some cream for the out side part but every time i have sex when my partner is penetrating it itches from inside burns and hurts a bit what can i do for it to go away? p.s i really don't wanna go back to my dr its embarrassing im like a weekly patient please help !!!