I think I have the exact same issue, I think the shape of my ears don't get a good seal on the earbuds.
The other day I noticed when pushing the AirPods into my ears a bit there was a much fuller/deeper bass and came to the realization I have been missing out on pretty much all of the lows and a lot of the mids on these things.
I searched for some kind of attachment that would get a better seal and I found exactly what I was looking for. These silicone earbud tips on Amazon.
I just got them in today and I feel like I am now hearing everything I was missing and the difference is huge and they sound amazing with the tips on. They are fairly comfortable. I never had an issue with the pods falling out but it may also help with that if you have that issue. The only problem is you have to carry around these things with you everywhere but it comes with a silicone key chain pouch to put them in. I was recommend giving these a try. They may not work for everyone but they have decent reviews and they definitely worked to fix this exact problem for me.