How can you tell if a guy really means it when he says "i love you"?

I love you before is to get , during is to thank you for , after is saying thanks, lets do this again real soon. The only for sure real I love you is when you get it after making it clear there will be no . If it's said "but I love you" it's just begging for sex. Any time you have to wonder if it's real it probably isn't