My two year old son is just fighting me on everything naptime discipline bedtime...?

My son has up til now been relatively an angel. We have a great routine since 8 weeks old and aside from a meltdown occasionally he is a good boy but the past two nights he wont let me put him to bed without screaming for me( he's been scraming in his room crying now 45 minutes hes tired), naps are the same. discipline is "mommy dont tell me no" I understand he is two but what gives with the shift in temperment? help please from a normally patient mom who is at the end of her ropes. Did I mention I have a 12 month old also...