-- Sex: Are you thinking about it enough.
-- Sex: Are you thinking of it enough.
1. Are these two sentences have same meaning?
2. What do these two sentences mean?
3. Can I use the second sentence instead of the first senteence?
Are you thinking enough about it?
Are you thinking enough of it?
Yeah, they have the same meaning. You can use either of them.
See my previous post. The two sentences, as written, are not the same.
You moved the word "enough" in your restatements and, in doing so, you ran into an idiom.
In the first, "Are you thinking about it enough" and "Are you thinking enough about it" are equivalent.
In the second, however, "thinking enough of it" is not the same as "thinking of it enough". "To think enough of something/someone" is to hold it/that person in sufficient esteem. "To think of something/someone enough" is to think of them with sufficient frequency.