Washington: Pop star Britney Spears has opened up about a troubling experience with Botox, revealing that the cosmetic procedure caused one of her eyes to droop for four weeks and left her feeling "so embarrassed," according to E! The "Gimme More" singer discussed the experience in a recent Instagram video, demonstrating how her left eye had drooped after, according to her, a doctor injected too much Botox around the area. "It's really bad, because the doctor put so much Botox in this left eye that it drooped down like that," Spears said while demonstrating the effect. Spears said the side effect lasted for several weeks before gradually improving. "The experience also affected Spears' confidence, with the singer admitting that she was "so embarrassed" by the outcome.