Student receives anal sex very painful

my boyfriend is bigger than me and has more experience sweeping, for this I always go and I allow them to do what he wants. In this way I learn more about what to do in bed, and I can also experiment. But I have to say that this time the experience was very painful. He wanted to do anal sex. Clearly, I have never had sex in the ass. But he told me that it would not have been at all painful. And that was a lie. I got on all fours and he shoved his cock little by little. Has not stopped, has continued to sink in with a lot of strength and the pain was terrible. We changed position and I again fucked her ass. And lying was the least painful.