我很好 vs 我不是很好
When saying 我很好, We don't use 是. But we use a verb when we make a negative sentence such as 我不是很好. Is 是 necessary in the second sentence or can we say just 我不很好?
Using “我不很好” to mean "I'm not fine" is valid. Usually, modern Chinese language adds "很", which literally means "very", in affirmative sentences; however, "我是好的" and "我好" are still OK and are mainly used to emphasize one side when comparing two aspects.
The weirdness disappears when it comes to negative sentences, so "我不是好的" and more simply "我不好" are both used widely. "我不是[很/太/十分]好(的)", "我不[很/太/十分]好" are used to soften the tone, just like in English, "I'm not [very/too/quite] well".
BTW, we have too many bimics here! Hello, @13bimic! ;)