If you're writhing on the floor, howling in pain over the splinter in your finger, you're being a tad melodramatic, that is, exaggerated, affected, or histrionic.
This term was first used in early-19th-century theater, as the adjective form of the noun melodrama, which is a performance piece featuring exaggerated characters with emotional appeal. Outside the theater, melodramatic behavior is also characterized by a kind of performance or exaggeration of emotions, but it's very rarely appreciated or awarded extra points for artistic merit. The common phrase "Quit being so melodramatic!" is a terse way of pointing out to someone that they are overreacting.