Hatco

I'm new to bass fishing. Been to castaic lake three times and each time I get a solid bite, I lose the fish somewhere in the fight without even seeing the fish come up to the surface of the water. I set the hook and start fighting the fish, the first time I was using a Carolina rig with a senko worm and the other times I was drop shotting robo worms. I fight the fish for a at least 2-5 mins and then *poof* it's just snaps my line right off. I'm using a ugly stik elite rod with a basic ugly stik combo reel and 8 lb. Berkley vanish line with the drag set. I'm not exactly sure what the setting is because I don't have a scale. I feel like I'm doing it wrong and it's very frustrating not knowing where to start. Sound familiar to anyone? Any ideas?