May I obtain a repairman certificate for my own amateur-built aircraft?
You may obtain a repairman certificate for your own amateur-built aircraft if you built the major portion of the aircraft. The only privilege this certificate gives you is contained in 14 CFR section 65.104, "Repairman Certificate - experimental aircraft builder - Eligibility, privileges and limitations", i.e., to do the annual condition inspection.
The privileges and limitations for repairmen are in 14 CFR section 65.103, "Repairman certificate: Privileges and limitations". To obtain a certificate, apply through your local FAA Flight Standards District Office.