Horrible headache! Please help

I've been struggling with this headache all day. They've become pretty consistent in the 2nd trimester. I'm 18 weeks today. I took my Tylenol to the office with me last week and forgot the bottle there. I know I'm not supposed to take ibuprofen while pregnant, but would it hurt just this once? I'm desperate for relief. I cannot stand or walk around without intense pain, so I can't go to the store right now. I'm laying down with an ice pack on my head which helps a little. Would taking ibuprofen just one time hurt the baby? Have any of you taken it while pregnant?