Dr thinks i had a postpartum cerebral venous thrombosis. ct w/contrast neg and mri without contrast neg. doc says still possible? even after neg scans

Check the scan type: I'm sure your neurologist knew exactly what type of scan to get if CVT post-partum was what they were looking for but you didn't mention it so I'm asking for a clarification. You should've gotten an MRV scan not an MRI & not a CT with contrast although that could've shown something if it were a big honker of a clot. If clinically, warranted he should go forward with treatment or get 2nd opinion