Headache!!

So I'm currently in my 2WW, 7dpiui. I've had a pretty much constant headache since Saturday evening that hasn't let up. I've taken Tylenol to manage, but the last two nights It's woken me up at 3am-6am!!!! Can this be an early sign of pregnancy? Anyone else experience this? We are TTC #1 so it's all new to me. (On a side note, I never ever get headaches..) any comments greatly appreciated!