What Causes Irregular Periods?

i took a pregnancy test like i do every month and like every other month it said negative. I took that in September. Well me and my fiancee broke up that month so when i didnt get my period i was thinking maybe it was just stress. Then i didnt get it in October. I was a bit confused. On November 2nd i bled for 2 days it was barely even noticable? It is now the 21st of November & still no period. I am very confused. I sleep all the time, very irritable, i have gotten sick maybe 3 times, and to top it off there has been two occasions where i have not been able to make it to the bathroom and im not talking about urinating either. Its kinda embarrasing. I have been trying to concieve with him for almost 2 years and nothing and now all of sudden out of nowhere this happens. I just dont get it? Is there anything you can tell me on this?