I'm sorry if I'm coming across as rude, I went to EJ to try and maybe find some simple answers for you, but they're holy paladin post is actually really good. There's a bunch of math and shit too if you're into that :P.

http://elitistjerks.com/f76/t110847-...ndium_4_0_6_a/

I would check it out, might give you a better idea of what to cast and when, because I know Holy Paladin is kind of one of those classes that's always been kinda easy to play, but hard to really be good at.

If you have a lot of experience in previous expansions with healing, but haven't really been exposed to it much in Cata, i can tell you its a lot different. I noticed on my druid that its really more about spending the least amount of mana possible, and knowing when to "blow your load."

After looking at your gear I'd say to reforge to some haste, or spirit if you're having mana regen issues, after giving EJ a quick browse your stat priority is Int > SP > Crit > Haste > Mastery.
Your spec is also a little off.

I hope I'm not being rude by telling you to go read EJ, but it is a great source, and I'm just trying to be helpful because I have played ZERO holy paladin in Cata, I have however healed all of the content minus hardmodes on my druid. I know when my friend started out when Cata first dropped he had issues, but then once he got more heroic gear it got a lot easier for him.