What does it mean if while on Ortho Tricycline, my period doesn't stop for over 12 days and normally I am consistent with a 3-5 day period (I have been on Ortho Tricycline for like 2 years).

Many possibilities--it could be a strange cycle for you and perfectly normal, it could be an indication of unintended pregnancy, it could be response to being on antibiotics. Might be wise to come in and have these possibilities reviewed.