When I was TTC my doctor told me I couldn't take anything for my low back problems (2 herniated disks). I was on Mobic at the time. He said that there was NOTHING I could take. (I assume this meant Ultram since I had also been on that at one point.)
I had back surgery in late December, but had been TTC'ing for the prior 3 months. We stopped for December and January when I was on pain meds and muscle relaxers, but picked back up in Feb. We got pregnant in March.
Check with your doctor ASAP.