Could he be sick?

whn i tickle my boyfriend (whether it be his feet, armpits or stomach or wherever) he tells me to stop cause he cant breathe and it hurts him mre than it tickles. he never laughs when i tickle him just rolls around. could he be medically ill? also, say if i were to tie him up and tickle him with no mercy could he have a heartattach, suffocate, and die? i dont want this to happen but is it possible?