Periods are caused when the egg goes unfertilized. You only have a period after you ovulate, all this provided you aren't already pregnant, seems to me that if you are only having a period every 5 months then you are only ovulating every 5 months. Not having a period for 5 months is very dangerous on your body, your hormones start building up, your uterine wall gets thicker and thicker. I would definitely go see a doctor preferably a obgyn to get help with your cycles, they'll also be able to help you with getting pregnant sooner. A lot of people say that a doctor won't help you unless you have been TTC for a year but that's provided that woman's body is functioning normally and it seems yours isn't. A doctor will be able to get you on something to help you cycle more regularly and my doctor, whom I just recently seen for the same reason, told me that that would involve starting on fertility pills. Which would be a win situation. Hope I helped a little!