Learned this today from a guy who knows a thing or two about startups: Don't worry if there's competition. Worry if there's no market.
Even if *you* did the work, use "we." It completely changes how you're seen as a teammate/leader - and the easiest change to make.
number one thing that's changed how I work: meeting successful ppl who say "we had no fucking clue what we were doing in first few years."