I had my period in july, august, and september then this october i didn't have any and i took a pregnancy test and it was positive but i didn't have sex or anything. i'm pregnant? i'm 18 and i've never had sex and i'm a virgin?

Normally regular women can skip a period or two occasionally and not be pregnant. If you never participated in any activity where sperm could enter your vagina, I suspect you did the test wrong & need to repeat it. Such tests are often falsely negative but rarely falsely positive.

If you never had sex, why did you do a pregnancy test? If you did not have sex, you are not pregnant. If you have any doubt, get a blood test for HCG level. Get HPV vaccine. Wish you good health! Safe sex: https://www.hopkinsmedicine.org/health/wellness-and-prevention/safer-sex-guidelines