I'd just like to point out for your newer students that the following example is in indirect form and not reflexive form:
Me duele mucho la cabeza.My head hurts a lot
We can tell the difference because it does not say "Me duelo", which would be reflexive form, in which the "yo" form of the verb would agree with "me".
Instead it says "me duele", which agrees with "la cabeza". We can see this if we change the order of the words:"La cabeza me duele mucho."
For students who do not know where the "me" comes from you can search for the lesson on Direct Objects.
