Well, your two choices are
1° Go to Dartmouth. If you don’t like Greek Life, don’t join Greek Life. For a big city fix, plan to study abroad in a capital city and see if they have domestic exchange programs, say, in NYC. You applied ED: remember your reasons. Surely, with so many excellent colleges, there are other colleges you could have applied to beside Harvard and Dartmouth, yet you chose Dartmouth. Look into your memory and reasoning system from back in September.
2° Withdraw and take a gap year. You’ll risk not having Dartmouth AND not having Harvard but you won’t have the regret of not trying for Harvard.