X-rays will not diagnose oral cancer, though they can be helpful in hard tissue cancers, sonograms work in some cases in stomach cancers if there is other symptomology that might support what they find, but they don't work for oral cancers. You can have no change in a normal blood panel (what you have had) and still have cancer. They need to be looking for specific markers which are a test unto themselves. The only way you are going to have piece of mind is though a biopsy. If you have a hard spot in your tongue that is a bad sign, and it wouldn't show up in an x-ray, but could be felt by some knowledgeable fingers, or picked up in an MRI or CT with contrast. The testing that you have been through isn't specific enough for what you want to be looking for. Perhaps what is going on with you is nothing, but as the posts above say...there is only one way to know for sure.