You rushed the game and went badly equipped into areas you are not supposed to go to at that stage. What did you expect? I mean you absolutely can do swamp in troll armor if you know what you are doing but plains no way.

Also judging from what you wrote I assume you also only had basic food items from foraging and not the best cooked food for the given area.

Many people underestimate how important food in this game is and people who tend to rush in order to prove how awesome they are often don´t want to spent time on farming turnips ect. Btw you find turnip seeds in the swamp in case you want to give it another try.