The TVTropes Trope Finder is where you can come to ask questions like "Do we have this one?" and "What's the trope about...?" Trying to rediscover a long lost show or other medium but need a little help? Head to Media Finder and try your luck there. Want to propose a new trope? You should be over at You Know, That Thing Where.
It's going to be one of the Unrequited Love Tropes. Given how many tropes surround this issue, usually you need another detail to it, such as how the two parties feel about it.
If you confess your feelings, and the target is like "What?! No way! I don't want to have anything to do with you, you creep!" Then that might be a case of Abhorrent Admirer.
If you confess your feelings, and the target says "I like you too, but romance complicates things and I don't want to wreck the friendship we have," then that might be Better as Friends or related.
There's a lot of directions to go on this, so there needs to be a little more info.
You confess your feelings, but they're not reciprocated.