Are b12 shots effective for ocd/anxiety? would it be good to take with and ssri?

Only if deficient: B12 deficiency can cause mental illness and might be a factor if you are deficient. However, if you are not deficient then B12 shots should not have a significant benefit. If your level is below 500 it is worth a try. See http://chriskresser.com/b12-deficiency-a-silent-epidemic-with-serious-consequences & http://kellybroganmd.com/article/b12-deficiency-brain-health/ & http://tinyurl.com/p5n6utk