、！。
Hey, this isn't funny! It's seriously rough, I'm telling you.
Literal
Wa-, laugh-matter is-not [よ]! Really tough is-[because-だから-さ].
Stuttered わ、笑いごとじゃないよ expresses agitation — わ captures a startled inhalation. 笑いごと ('laughing matter') is a fixed idiom, typically in the negative 笑いごとじゃない ('it's not a laughing matter'). 大変 ('serious, major, tough') is the general-purpose intensifier for bad situations. から at the end serves as the reason-providing particle, softened further with the casual filler さ for insistence. A bouncy, flustered protest.