I feel something with my tongue on the right side of back of mouth on my gum it feels like a line been there for a week it usually disappears in past?

Could be Infection: Many oral conditions affecting the soft tissues come and go. Some are harmless, but others can be quite serious. Many of the most common soft tissue changes are completely painless, even though they can be serious, such as cysts, tumors, abscesses, and infections. Any lesion which does not completely heal within two weeks should be regarded as potential dangerous. Get it checked by a dentist now!

Swelling: Swelling that comes and goes should be investigated. Call your Dentist. Report the problem. Make arrangements to be seen the next time the "line" is prominent.

Possibly a callus: A linear whitish raised patch of skin on the inside of your cheek that lines up with where your upper and lower teeth meet is most likely a callus formed by habitually chewing on your cheek. I see this very commonly and it isn't pathological but it is essential that you get it examined to be sure. Don't avoid exams fearing the worst as most often it isn't!