Monica appeared to faint in the middle of her concert in Houston on Saturday night. Video shows the "Angel Of Mine" and "The Boy Is Mine" singer collapse on the side of the stage before a crew member rushed her away to an ambulance. “They’re saying Monica left in an ambulance after passing out by the stairs,” one user alleged on social media, adding that something “seemed off” with Monica throughout the show. Her reps have yet to comment on the incident, so details remain unclear, but the singer has been open about her health struggles in the past — including a heart problem that affected her on tour when she was 18. The now 43-year-old has also been hospitalized for high blood pressure and endometriosis in the past.