That may be part of your problem. Are you using ad variations or are you actually changing out the ads and running one at a time?
sometimes patients is key. It takes time for your ad to move throughout the system so if you are changing the ad constantly (5-6 times a day) you’re not getting full delivery of your ad in the system.
Best practice would be to write 2-3 ads and let Google rotate them automatically. then let it run like that for a while, at least a week.