In my period I have 2-3 months bleeding. Rarely it happens in a normal cycle. I have gone through ultrasonography and thyroid test. Both normal. I will get married soon. Will my problem be an obstacle for pregnancy?

You bleed for two - three months or your periods are two to three months apart? An important distinction.

I would try for a baby and if pregnancy doesn't come in a year or so then consult a doctor.