Why does my tooth still hurts after 3 months of a root canal and crown?

Thats not normal, root canals should be something that makes the teeth do not hurt,but technically speaking when we perform a root canal, we just remove the 80% of the pulp of the tooth, so there is always a chance of either a secondary pulp conduct, or an accessory conduct.provably what you need its to have another look at the root canal.and also another thing,could be a high spot that its touching first from the other teeth,this may cause that this tooth will hurt, a clinical examination would be your best choice and also percussion vertical and lateral.