can anyone tell me where is the best placy to buy a basal body thermometer. i looked on ebay and the like but there are so many to choose from its hard to know which one is the best. i read on one site to go with one that measures to 1 decimal place then on another site it said 2 and not to touch a thermometer that only does to 1 decimal place. im comfused. do i need to spend alot of money on one or will a cheap one do. and also when i use it when will i know for sure that my temp has increased. will it be a big jump??