I hurt my back 2 mos ago and still have pain. Mri spine was normal and diagnosis is muscular. Is it possible to have a disc problem with a normal mri?

Yes. It is possible &there are other structures that can also be injured & play a role including joints of the spine known as facet joints. Return to normal status can also be a function of the age of the spine & one' s underlying physical conditioning including weight & medical health. Habits like smoking play a role too. Prior history of back issues can also play a role as well as other reasons.