Pre Natal vitamins

Me and my husband have been together for 8 years, married for about 3 weeks. We decided that when my birth control month was over(another 2 1/2 weeks) that I would stop taking them, to get them out of my system. Then when we buy our first house(hopefully in the next 2 months), we would officially start trying to get pregnant. When do I start taking pre natal vitamins? I've seen that you take them also when your trying but I don't know if I should start them right when I stop my birth control, or once we actually start trying....