Flat head :(

At my twins 2 month appointment doc said it looks like their heads are getting flat on the sides. He told us to make sure we offer tummy time as much as possible to prevent further intervention with helmets etc. they are 9 weeks old and they still sleep oftennnnn. They are awake maybe an hour before crabby and ready for a nap.... after they eat and change and burp a half hour is already gone (even longer if I’m alone). AND we all know babies only last a couple min on their bellies.... anywaysssss, does anyone have any ideas for me? I feel so sad like I’ve just kept them in their mama Roos too long to sleep and that’s the problem?? If they sleep on their backs in their beds then they still turn their heads to the side? Same if I put them in their bellies...... so how do I help that if they’re asleep over 15 hours a day/night????

Sorry, I just feel like I failed them 🥺😟