Ok, you are saying "You know I love you". The string that you need is "I love you".
Then contain cheks if the message contains the needed string, so that's: "You know I love you". It just checks if the needed string is somewhere in the message, not if the message is the same as the string you want.
So you need equal - it will check if the message is exactly the same as the string: "You know I love you" won't pass this time, because there is also "You know ", which you don't want, so the funtion will be called only if you type "I love you" (nothing more, nothing less) - that's what you need.