lisjay, the best thing to do would be to temp for a while. That will help you get an indication when you usually ovulate, and then you can use OPK's for the week around ovulation to help pinpoint it more accurately. The length of your cycle on its own doesn't give a clear indication of when you ovulate, because you may have a long or short luteal phase (the part of your cycle after you ovulate) and therefore ovulate before or after the halfway through your cycle mark. There is heaps of info on this site about temping and charting - have a good read, get yourelf a thermometer and have a go.