by behaviour and attitude.......
Just follow your heart and you will find the answer
Stab in the dark here but.... ask her !
if they are constantly flirting with eachother
find another girl!
It wouldn't be wise to marry someone who doesn't love you. Find a girl who loves you. I am sure you will find one!!
The next thing to find out is, since he loves you but also has a girl, who does he love more, you or this other girl? If he loves her more than you, don't waste your time with him. If he loves you more than her, perhaps the two of you have a future together.
If she always looks at the boy, and is shy towards the boy.
EASY! 1. Treats you differently. 2. Plays with you.
Someone that cares enough to find out who she really is & then loves her anyway.
In Google.com you van find almost everything!
Maybe he doesn't really know that he loves you.