If you have been trying to concieve for a while, you may be getting a bit stressed and this can effect your cycle. Have you been to see your doctor? That really needs to be your first stop, you don't say how old you are, but if you are over 30 and have been trying for over a year, I would ask for a referral to the fertility clinic. It is perfectly normal to take that long to concieve, but you can sometimes wait a while for an appointment, so it is best to ask early. They will not entertain you unless you have an indication of other problems (which your periods may indicate) or if you have been trying for at least a year. I have always had very erratic cycle unless I was on the pill, so ended up getting a referall after a year, I waited 6 months for an appointment, went through 6 months of tests to be told everything is fine then I got pregnant the next month! I then ended up with a 2nd 13 months later as we were sure that it would take 2 years again and a 2-3 year gap seemed perfect!