I am 49 years old and i had not had a period in 15 months and then yesterday i started again, should i be concerned?

Yes, u need evaluati: Evaluation, it could have been your last period, but the rule is if you have not had a period for 12 months - that is menopause, so you had post menopausal bleeding which needs an exam and an ultrasound and u may need an in office( that is where I do mine on my pts. ) hysteroscopy and endometrial biopsy to make sure u have nothing strange going on with the endometrium.