Took bcp for 32days before starting triptorelin for ivf . on day 9 of the injection my menstruation started . is this normal?

Probably yes: This sounds like you are describing a "down-regulation" cycle, in which case this would be approximately correct. I'm having to guess that you are down-regulating, if your doctor had a different protocol in mind, this might not be as intended. Check with your doctor or feel free to resubmit here with more information about your intended stimulation plan. Good wishes.