Blood sugar levels

Took it today for the first time alone. And my fasting # was 36 after eating breakfast was 28. Seen my Dr today she said that was way to low should be 60-90 fasting ...has this happened to anyone? Waiting to here from my Nutritionist. I changed my eating habbits kinda drastically. But after seeing my Dr she said to go ahead and eat Norma just no sweets ...so did and took it again now its 101...which is good. Had to be under 130...maybe I'm not doing it right?