Try testing right before you eat, then 1 and 2 hours after you eat. That will let you know what that particular food(s) do to your glucose. Try to keep your carbs to 45 or less per meal. Snacks to 15. Learn to read labels, the carb counts are on there, along with serving size.

If you start to feel funky do a quick stick. May explain a high or low.

On lows. 70 or lower is considered a true low. That 58 you posted was a real low. Treat with 15g fast acting carbs, wait 15 minutes and re test. If you have been running high 180 or more, as you come down it may feel like a low. Try to hang tough and ride it out. It will get easier.