@Romper I love that finger in my ass too! My baby started doing it to me several years ago. His thumb feels the best and he says that it's easier to get in than a finger. And I only need about 2 inches to get off or make it more powerful.
When he puts his thumb in does he push down and rub your colon wall against his cock while he’s fucking you. I did that to a woman once and she had a leg shaking orgasm.