why, as a gay guy, do I only like strait boys!

so there's this guy at my school and I love him but he just broke up with his girl friend because he liked another girl and he always asked me for advice, this. is. torcher! I don't want to kill our friend ship by trying to see if maybe there was some possibility he is bi. I've considered becoming trans for him but I know that wouldn't do anything as he would know it was me so what do I do? I would love advice, and just for reference I'm only 14 and he's only 15.