About Riba

In 2006 I brought a car on installments from a conventional bank. I do not remember what my thought process at the time was and why I made that transaction. Perhaps I was careless towards the rules of sharia or perhaps I didnot consider riba haram which is doubtful but I cannot be sure. What I do know is that if somebody had me if riba is haram or halal, I may have replied that it is haram. In other words I do not remember what my thought process was.

4 years later in 2010. I got married. I am now worried that IF in 2006 I considered riba halal, then I would be out of the fold of islam. Although I continued to live as a muslim, praying (not regularly unfortunately) and fasting, how would that have impacted the validity of nikkah ? Do I have to repeat the nikkah ?