weird feelings in head

Hi, I have been having weird feelings in my head for a while now. It isn't pain or anythings, just i look at a wall or concentrate on something and it looks like it is kind of moving. I don't really get dizzy, but it is just a weird feeling in my head. It does it the most when I am working. I have to really concentrate on it to get the full effect. i don't have seizures, vomit, nose bleeda, weakness in the body or anything. I just have weird feelings in my head. It doesn't do it all day, just different times during the day and night. I am worried it could be a tumor, what do you think?

Thanks