Stop only changing your ads
Here's something you should try next: instead of always changing your ads and creatives, try changing your landing page. I don't mean a full revamp — I mean the top fold, the top one-third of your page. Change the headline, change the image, change the CTA in that section. You'll be surprised what kind of difference that makes to your conversion rates.
Focus on the top fold, not a full redesign
Ads are very, very important, but at some stage you also have to look at whether your page needs some work. You don't have to change the whole structure — everything happens at the top. The most important part is the top.
What to change: headline, image, CTA
As long as you change that top third of your page — the top of the fold — you might start seeing better results.
Test your page, not just your ads
So next time, don't focus only on the ads. See how you could also optimize your page.