My eyes can't focus on one spot?!

I've noticed a problem that is bothering me lately. I can't make my eyes directly focus dead center on one spot. When I try to, I notice that my eyes look slightly upward from the spot I'm trying to direct my focus. When I say I can't focus, I mean I can't center my line of vision. Nothing is blurry, and I can read just fine. I just can't focus and center my line of vision onto one spot. I don't know if this is normal, but it definitely bothers me a lot. It's literally IMPOSSIBLE for me to focus my eyes where I'm trying to look.
Obviously I need to see a doctor about this, I'm just wondering if anyone can give me some ideas for what may be causing this.
Also, when I cover one eye and try to focus with just the other, it's even MORE noticeable. My eyesight starts to shift upward even more noticeably. I don't know if I'm explaining this well, I just feel like I'm not able to completely connect to anything I'm looking at with my eye sight. It's weird...