Being too focused on distracting yourself from your situation led to you not noticing what the pig was doing, until it rolled onto you.
The pig kept struggeling on top of you, until you tried to push it off.
You weren't able to push it off due to your current state, but seemingly made it notice you.
It surprised you when the pig suddenly pressed itself against you and made you redouble your efforts, which only seemed to make it more interested in you. The pig wound itself around you like a snake, seemingly having already adjusted to its new body.
The sensation of the pig's soul squeezing and grinding against yours gave you a strange pleasurable feeling.
You tried to ignore it and untangle yourself from it, but the feeling kept growing, until you found yourself subconsciously reciprocating.
Nothing could take your mind off what was happening or untangle you, so you gave up and started actively winding yourself around the pig's soul, just like it was winding itself around yours.