How to track ovulation?

how do you track ovulation when u don't get a monthly period im 29 i got my period in dec 2008 and again in july 2009 that was six months apart my periods are like that most of the time only two or three a year my doc said there dosent seem to be ay problems i do have one child he's seven so i know i can get pregnant but we would love another any suggestions would be grateful thanks in advance tracy