Fingering your butt ?

A few days ago my boyfriend and i got frisky and he started fingering me. He was doing it and it felt amazing. He was fixing his hand to grip more so he can go deeper and he somewhat entered my asshole but not far, basically just surface. He asked me if he did and i said yes but i loved that feeling and don’t know how to tell him. He told me that he wants to put his thumb in my ass while fucking me and I thought i wouldn’t like it because I’ve heard stories about how it hurts from anal and so i didn’t know what it would feel like with a thumb. Anyway , i kinda want to try it now. I guess my question is, have any of you ladies been ‘fingered’ in your asshole and liked it and what does it feel like? I know women who have had their SO do it to help them before anal.