Yes,, they do mean the same thing as long as you complete both sentence (especially the second one) because they aren't complete sentences. You're just phrasing it in a different way. So for instance, you would say "I can't help thinking that...." And finish the sentence so it makes sense and has a context. Hope that helps!

Just like any other culture and language, there are always subtle differences (like how you pronounce your vowels and consonants and how hard or softly you stress them) and dialects because of where a person lives. And although these are not always the case, generally you can figure out where someone lives by the way they speak. I won't really go into detail on this because for many, it's considered rude and stereotypical, but I will use myself as an example. For instance, I live in the Midwest U.S. and my accent (and I have been told this by many different people who are not from the U.S.) is almost the LACK OF an accent. I live equal parts away from the Western states and Eastern states so I don't have either one of those accents muddled in. I hope this helps.

When you say "you are interesting" it means that you find them appealing, funny, and the like. When you say "you are interested", that implies that HE is interested in YOU and a question is generally implied...So it sounds like you're asking him if he finds YOU interesting. If you think this person is funny and makes you laugh, that would be a better way to phrase it. Just be more specific and your point will come across better.