D/c'd wellbutrin (bupropion) 4 weeks ago while tapering off 40mg celexa (trying to get pregnant) period is 1 wk late and all pregnant tests neg. cycle always 28 days. could my late period be r/t stopping those meds?

Possible: Both medications are so called centrally acting substances, with possible indirect effects on your hypothalamus and pituitary gland, where the regulation centrum of your menstruation resides. I do not observe these effects on a regular basis, but it is certainly possible.

Possible : As these medications can affect Dopamine and serotonin, it can affect the pituitary hormones that influence periods including and most notably prolactin.