the first verse describes a state of euphoria past hurt similar to being broken in by a dick and it hurting for a while but then it feels good. The repetition of her “lovin it” suggests she is trying to reinforce that she is feeling pleasure and should stick with it despite pain
The second verse utilises the verb “tears” as a metaphor for lubricant thus she has “ran out” of lubricant but as we see the lack of such does not prevent anal pleasure as she goes on to state she “like(s) it”
this next verse tackles the unwillingness to continue when her anus is pierced. Blood is possibly “comin out” but she silences herself as she knows the pain is temporary “can’t stop so shut your mouth”
This last verse, hotly debated by critics, seems to be about a potential anal prolapse or tear due to the “colors in” her changing enough to be pointed out”