Hi cep, I think it's great that you are so aware of who you are and don't feel the need to sleep with men to "make sure". I absolutely believe that knowing you are gay is intuition. We find out way before we are old enough to sleep with anyone, man or woman, or anything in between. I think you should tell your family and not be afraid. I have had many friends in your same place, and the mistake I see people make over and over again is that they give their family the power to determine whether they can be happy and have peace of mind. What I mean, is if you go to your parents and approach the situation with fear of their reproach, then they may try use the power you give them to try to affect your emotions and/or confidence in your decision by making you feel bad, guilty, or shameful. Maybe your parents are not that type of people, but regardless, I would encourage you to approach the situation fearlessly and with confidence. Like you learned with your friends, anyone who really loves you will love you no matter what. Love is not conditional. People who love you will love you for who you are, not who they want you to be. And remember, your parents are not always the people you want them to be either, but you still love and accept them anyway. Also, you are not only lesbian today or tomorrow when you come out to your parents. You will be lesbian for the rest of your life, so the earlier everyone gets used it, the better. Good luck!
I support your decision 100%! Be true to yourself against all odds is my advice. What's the use of a life half-lived? Unless it's beneficial to you that your family is just kept in the dark. In which case, leave them in the dark.