Why are my fasting blood sugars high when I have an a1c of 5.7?

My a1c was 6.2 about 1 1/2 years ago. Since then it has gone down, with the most recent one 5.7. However, I typically have high fasting blood sugars on my meter, such as 130 or 150. It varies but is almost always over 110. I get some high readings on my meter throughout the day but never higher than 200. I seem to have more trouble with my sugar feeling too low during the day and I need to eat frequent snacks. I had a low blood sugar combined with heat exhaustion 2 weeks ago of below 70. I don't understand why my blood sugar fluctuates as much as it does. First thing in morning it will be high, then a few hours later it will have gone down. I start to feel shaky when my blood sugar is below 90. I really try to eat healthy meals and not go too long without eating, but doesn't seem too change. I'm happy my a1c has continued to go down without medication but I don't know if there is something else going on here! Any advice?