Nauseous but why?

I've been nauseous every day for the past four days, which is out of the ordinary. I had like a two day period last week, ending Thursday. Is it crazy to think there was implantation bleeding and now I'm feeling symptoms of pregnancy? I haven't taken a test yet...it's just such a bummer when you're TTC and every little thing makes you think, could this be it? I'm nervous to take a test because I'm convinced it'll be negative but hoping there's a chance it'll be positive.