Why isn't he telling me he has a gf?

If he has a girlfriend, he's not available so what's the problem?

You are still young and so does he so just let him plow as a many holes he wants 

He’s not your husband so do what you supposed to do with many guys you will have sex down to road

Your friend is keeping Eva a secret from you because he knows that if you were to see the two of them together, it would throw you into a terrible rage of jealousy, and in the heat of the moment, you would challenge her to ritual combat in front of your tribe, and that she would be forced to accept, lest she be cast out into the wilderness, where she would be consumed by shadows and become a hungry ghost, haunting your tribe's nightmares for all the generations to come. It happens frequently and your friend is alert to this threat.

Your course is clear. You must inure yourself to the latent desire which you have towards this man, so that when at last you see them together, you will not be owned by the fire in your loins and the hatred in your heart. Speak to the wise women of your tribe about casting a spell upon him which will twist his back, turn his words to mush in his mouth, and his hair to fall from his head like an old man of thirty whose grave yawns open beneath him like a hungry maw. Let his visage disgust and terrify you so that when you see him with her, you will know only pity and regret and disgust rather than the consuming desire which he sees in your eyes when you look upon him. Then and only then will he trust you enough to speak to you in slurred and halting words about this woman, and your friendship may once again prosper.