Is it possible to have arachnoiditis and have it not showing on a mri? i have all symptoms but mri was normal?

Yes, it's possible: Mri is reported as being highly sensitive and specific in detecting arachnoiditis, however, there is a small false negative rate associated with the condition. A ct myelogram could be done as well as an EMG if the MRI is negative and clinical suspicion remains high for the diagnosis. Talk with your neurologist and see what their recommendation may be.