Linda, I am so sorry to hear Molly is struggling. Did your vet mention FCM? (Fibrocartilaginous Embolic Myelopathy). That is pretty common in larger dogs and the prognosis is often good with time. Of course, you need an MRI to definitively diagnose it. Is she painful? Disc disease is generally very painful, while FCM is more true weakness – doesn’t hurt, the legs just don’t work. Hope she continues to improve!