Singer Jordin Sparks has gone four days without a proper night's sleep after she was struck down with a crippling bout of vertigo. The No Air star has been battling the dizzying condition since last week (ends26May13), and she has been resting up at home over the Memorial Day weekend (25-26May13). However, Sparks admits the dizzy spells have left her feeling uncomfortable and unable to sleep. In a post on Twitter.com, she writes, "I have not had a solid sleep session for 4 days. I have a serious case of vertigo. Dizzy when I'm up & dizzy when I'm layin (sic) down."