Ten days is a short luteal phase and may indicate a problem with ovulation.  The first line treatment offered for problems with ovulation is Clomiphene (Clomid) which makes you more likely to ovulate each month. One word of caution when testing for ovulation is to use the predictor kits as instructed by the manufacturer. If you do not follow the instructions correctly this can give spurious results. I would suggest that you keep a record of these tests to take to your doctor if you decide to seek help in trying to conceive.