Hi K.,
I'm an NFP (Natural Family Planning) instructor with the Couple to Couple League (www.ccli.org) and the thermometer we use in our classes is on this page: http://ccli.org/shop/onlineshopping.php?criteria=category...
You'll have to scroll down as it's third from the bottom. All our NFP materials are there too if you're interested in learning. We have teachers throughout the country who teach regular classes and there's even a home study course.
As for charting your temperatures, you do have to be very consistent with taking your temperature every morning. You should take your temperature at the same approximate time if possible. Thirty minutes before or after won't affect it that much, but if it's an hour or more off the usual time, it will likely be higher than normal and it's considered a "disturbed" temperature for that reason. Also, you need to keep activity to a minimum when taking basal body temps. That means it's best to take it right when you wake up before getting out of bed and moving around. Remember also that certain things can disturb temperatures or make them either lower or higher than your normal pattern. These things can include illnesses (fever), stresses (upcoming wedding, kids), vacations, lack of sleep, waking up a number of times during the night (example: sick child), varying bed-times (thus affecting hours of sleep), wearing different PJs to bed (thermal ones for example), turning the heater or AC on for the first time each season, adding a new blanket to your bed or sleeping without them, etc. All these things can affect temperatures although usually they're a one time event and you can pinpoint them when they occur (except things like stress which can be off and on). Also like one person already mentioned, charting temps can seem really hectic the first couple cycles, but generally over time you'll get in the habit of it and you'll start to see the pattern of low temps prior to ovulation and higher temps afterwards emerge. Finally you also mentioned having just come off the pill. We tell women in our classes that oftentimes it takes up to 3 months for the hormones to fully leave their systems and for their bodies to get back to normal, so that is another reason you may be seeing irregular temperatures because your body hasn't gotten back on track to produce estrogen and then progesterone (the two hormones of the female cycle) in order to jump-start ovulation and thus the ovulation sign that you are looking for (the thermal shift in basal body temperature). So you may have to wait a couple months to start seeing more regular temperatures and to actually see that thermal shift occur.
Hope that helps! Our website at the Couple to Couple league also has additional question/answers about NFP and what it is for your information.
Good luck,
M.