Wounder's

Me and my fencé has been trying to have a family for almost 3 years with two scares and I went to doctors and all is good one what they say because I'm only 26 my periods are not regular haven't been since I was 12 ish I smoke cigarette ' s even quite for a year or two so don't think it's that and from know of my family don't have that problem any advice on how I can or might can?