You’re just tight. It’s the default, you’re not weird. If you want to bottom, you need to start training. Basically, stick toys/plugs in your butt more often. Start with smaller ones and with your way up to larger ones with time as you get more comfortable. Plugs are great because they teach you to get used to penetration with a wide object but the base is narrower so they’re more comfortable for longer wear.

The other thing I’ll add is even when it’s not painful, bottoming can still feel uncomfortable at first. You kinda just have to get used to it before you’ll start enjoying it. Take it easy and remember you’re in control—there should be no pressure from yourself or anyone else to do anything you ultimately don’t want to do. It’s up to you. Happy bottoming!