Is it true I can't have sex for my first year?

No, that's not true. NA has no opinion about your personal life decisions.

"We are not interested in what or how much you used or who your connections were, what you have done in the past, how much or how little you have, but only in what you want to do about your problem and how we can help. The newcomer is the most important person at any meeting, because we can only keep what we have by giving it away. We have learned from our group experience that those who keep coming to our meetings regularly stay clean."

Narcotics Anonymous Basic Text 6th edition, page 9