Honestly you'll need to give us more information if you want a more correct reply.
You need to tell us what you're using for weapons, talents, which tree you're going and your rotation of spells.
If you're elemental and relying on your spells, then yea you're going to run out of mana faster than enhancement. Reason being, well you're relying on your casting spells to kill them thus more mana is used. Wacking with a weapon doesn't require mana. d(^^)b
At your level I would be using a one handed weapon and shield. Staves and other weapons won't put out good damage. Mind you this is for enhancement spec.
Using a shield will increase your armor and survivability. Once you hit 21, I believe, then you'll be able to use two handed axe and maces. This will allow you to kill faster, but if you feel your survivability is still low go for one handed weapon + shield.
Make sure to position yourself properly, such as close enough between two or more groups of enemy but far away enough so you wont get aggro. If you do this then you wont have to recast your totems as much. If you do this right, then you can pull mobs to you with Lightning Bolt and you'll be in range to obtain your totems effect.
At your level I used the Rockbiter for my weapon. If you pull more than one enemy drop a Stonclaw totem and kill your main target. If not then put down a Strength of Earth totem to kill your main target faster. Getting hit too hard? Put down a Stoneskin totem.
As a Shaman, especially at your level, you'll need to learn how to use your mana effectively or else you'll just run out of mana after every battle. Remember you're not a mage, so don't be trigger happy.
Start a fight with two Lightning Bolts followed by a Flame Shock. After that just pound away with your weapon. Throw in a Earth Shock if you still have a good amount of mana left. Ofcourse make sure you have the necessary totems up suited to your situation at the time. One thing about Shaman is that you need to learn to use what totem at what time.
Be careful about Searing totem. It's a very nice totem but remember you don't control who it hits. Sure it might start hitting the target you're hitting, but after that target dies it will shift to the next target if it's close enough. Your totem wont wait for you to be ready to fight, it'll just shoot anything in range. So if you're not ready to fight, you better start running hahaha.