Does endometriosis always affect your fertility? i'm only 20 and would like to have children at some point, am i better doing this soon

No: Approximately 40-45% of women with infertility problems have endometriosis. However many woman conceive with endometriosis, and after surgical or medical treatment. The goal of tx is to preserve your reproductive organs w/out damage to increase success of conceiving, also helping with the pain. Don't jump into trying to conceive until your emotionally , financially prepared to have children.