Why is it that when I'm feeling down I wanna call him to come over?

my guy friend, who is presumably still engaged, has been trying to get me in bed for the longest. i have turned him down repeatedly, but lately when i'm feeling my utmost down, i have the urge to call him to take him up on his offer. why do i feel this way? a man who i am really attracted to is now seeing someone else, and whenever i see him with her, it makes me wanna call my engaged friend.