Classic New player: warlock mana issues (WOTLK classic)

So I am new to WoW (level 25) and when I am killing mobs or in a dungeon, I'm constantly running out of mana. I play an aff-warlock, I put my dots on everything and use shadow bolt or rain of fire to keep my DPS consistent. I feel like I'm constantly having to sit and drink way to frequently in dungeons, more than the rest of my party. This happens every other pack. Am I doing something wrong? I hate seeing everyone go for the next pack while I have to sit, I feel like I'm holding them back and I want to improve. via /r/wow https://ift.tt/VQDJulU