Charting your Basal Body temp is a far more accurate way to determine if you are in fact ovulating and if so when. OPK's detect a surge in the LH hormone that indicates you are LIKELY to ovulate in the next 24 hours whereas a spike in basal body temp tells you that you have in fact ovulate within the LAST 24 hours. Using the two together is a very reliable way to determine when your most fertile time is. This is useful both for getting pregnant or for trying to prevent pregnancy.
YES hormones are a big pain! If u are trying to get pregnant try an OPK test ther really work!
Have you recently gone off of a hormonal form of birth control? Are you under any excess stress or have you recently been sick? All of those could affect your cycles. It wouldn't hurt to see your doctor and find out what s/he would advise.