I'm currently on 225mg venlafaxine , my period has gone from fairly regular to roughly every 2weeks, for past 1 1/5 months. should i be concerned?

Do have an exam: Don't be anxious or fret if that's what you mean by concerned. But do have an exam. It's not likely to be related to the anti-depressant, but they do some strange things to some people. Let your doctor see what's going on. Mention all your meds and anything else that might be new in your life. I hope it's a simple thing and you get it straightened out. Best!