Quick question, can a cleric change his domains? The domain I want to switch to is within my deity's domain list, so I don't need to switch faith.
There is an optional rule called retraining from Ultimate Combat supplement. Keep in mind that this is from supplement and this rule is optional even if your DM actually applies that book, so consult your DM before using this solution.
(Excerpt from Retraining in Pathfinder SRD. Emphasis mine.)
So, if retraining rule is allowed, you can change your Cleric domain by retraining. To do so, you need a cleric who has the domain you desire and has more levels in Cleric than yourself. It is unclear whether the trainer must have the same faith as yourself, but I assume it is the case.
I wasn't able to find anywhere else where you can change your domain. So, I think retraining is your only call.