1. Meters and Strips are allowed a 20% variation in the US. I assume you are in the US. When you factor that in, your 124 and 158 is not that far off. Should be better.
2. Make sure your hands are clean. When you get a "off" reading, wash and test again.
3. Finally, meter are cheap. You can probably get a free one by calling the maker or from your doctor's office. The money is in the strips. So get another one to double check or as a backup.
Hope the above helps.