Hi and thanks for using the forum.
It is not uncommon to have an "off" period every once in a while. A lot of factors can affect your menstrual cycle including stress, weight loss/gain, change in diet, change in exercise routine, thyroid problem, etc. It is a good idea to follow up with your doctor and make sure that everything is OK. IF you are trying to conceive, you want to make sure that you are actually ovulating. Your doctor can do blood work to check and see if you are.