I guess it depends on the depth of your suffering. The two words aren't really realated, nor even, in their primary, historical definitions, that near to being synonymous.

Bathos: http://www.bartleby.com/61/28/B0112800.html

Pathos: http://www.bartleby.com/61/21/P0112100.html

Must is they've sort of fallen in to each other through apparent similarity.