Middle back right side of tongue has a reddish smudge on it.. about 1 long, no pain.. seems to get better and then come back, could this be from something i am eating, im kinda worried it could be cancer, would cancer go away and come back?

Oral cancer would not resolve and then return, so don't be too concerned about cancer. You may be experiencing geographic tongue. Web search for more info.

I agree that the lesion which comes and goes in middle of tongue should not be cancerous,but you should see your Dentist . It might be plaque and bacterial deposits on the tongue which needs to be scrapped by Tongue Blade after each brushing