I had a saddle block yesterday for my cerclage. It took him a long time, now I have severe back pain--worse when I bend even a little. Is this normal?

Should get better! Sometimes the spaces between the backbones are tight, and all of us occasionally have trouble inserting a needle for spinal (saddle block) or epidural anesthesia. It's normal to have some bruising or tenderness at the insertion spot. Use a heating pad and acetaminophen, and don't be afraid to do gentle stretching exercises if ok with your obstetrician. It should feel better in a day or two.
It can be. Sometimes"technical difficulty", due to a number of causes, results in multiple attempts, locally bruised tissue, the end result being discomfort in the area. It typically resolves over a few days.
Probably not serious. This pain is probably due to the local irritation from the needle used for the block. It should be short lived, and is best treated with a nonsteroidal like ibuprofen. If it persists, or is accompanied by fever or numbness, tingling or weakness, it should be further evaluated.
Probably expected. A saddle block is basically a spinal tap with medication pushed into the fluid around the spinal cord. It sounds like yours was difficult, requiring multiple redirections of the needle to find the space. Since it was recent, it is most likely pain from skin bruising and will heal with time, ice and tylenol (acetaminophen). If you develop weakness or numbness, call your anesthesiologist immediately or go to er.