Was wondering if i am bad at this game.

Even on casual, if you're not maximizing your play style, the game can and will be daunting. Try and memorize where enemies are/appear in maps and learn to take them out as quickly as possible. Replay early maps to get used to ranged and close combat, learn to block and roll and pretty much try to play at least one map where you take no damage at all.

You shouldn't be whipping through potions so much if you're killing up a storm and not letting the enemies get close enough to hit you. Well, maybe mana potions if you're using spells a lot (which helps in some missions)...
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"Listen to a fat man when he tells you what to eat!" - Joe Tuna