It would help to start watching what types of food you are putting into your body. A regular exercise schedule wouldn't hurt either. You can change your body type. Trust me. I did it.
Sweeney Todd is a great one as someone else mentioned. A lot of Sondheim leading roles or large roles in ensemble shows don't need super handsome/beautiful people.
I love Sondheim.
"This ocean runs more dark and deep than you may think you know...I'll be the fear of the fire at sea."
-Marie Christine
"1776" -- an entire cast of men where good looks matter not a whit! Adams should be short-ish, Jefferson should be tall-ish, Franklin should be... well, Franklin-ish. But otherwise, a show in which physical appearance counts for much less than talent.
Trust me, it's better to be a character actor. Although more times than not you will be playing a supporting role rather than the lead, there are plenty of leading roles out there for us non-dashing types. And remember, there's only ONE leading man, but usually several supporting roles--more casting opportunities!