Don't wait! Talk to your crush sooner rather than later.
As an adult, if you're interested in someone, just say something. I learned this the hard way at the gym.
I thought a guy was into me because he was always staring, making eye contact for months, and often lingered near me. He even seemed to get jealous if other guys talked to me. I once even caught him trying to take my picture.
Yesterday, I finally approached him and asked for his number, only for him to act surprised and tell me he was married. I might have misinterpreted his behavior, but either way, I wasted a lot of time wondering. If you think there's mutual interest, speak up. It saves you from uncertainty and helps you move on if it's not reciprocated. Good luck out there!