Naw, you aren't fat. If someone would call you that, then it's his/her own problem, it's nothing you ever should listen to. Same for the people who runs those "terrible cosplays" blogs, that would be their own problem.
I think your cosplay idea sounds great. Keep going for it, and hope only for the best!
An guy who likes hacking into videogames for unused and bizarre stuff. Also a big fan, and supports as the one and only love couple.