You obviously don't have perfect pitch. Don't feel bad, neither do most of us. But you can acquire what's called relative pitch. I pretty much can do that more often than not. Try to get a song or scale permanently set in your head. Use the song or scale as a reference. With practice and hearing lots of tunes in a similar key, you can get pretty good. Of course there are classes that can teach it to you and I'm sure we have others here at SZ who can give far better advice. Good luck.