manic when gay/depressed when straight

before i write anything, i still acknowledge i am a bisexual, and i realize my preferences change overtime. i accept those things, and value bisexuality overall. now, i've noticed for a long time that whenever i'm more in the mood for someone of the same sex, i tend to be in a manic mood. the thought of being with a guy excites me. this has not been approved very much by society, but dammit i assert my right to find some kind of intimate happiness with a guy, and i'm going to find out it can be a great time. when my preferences lean to the opposite sex, i get depressed and hopeless. yes, i'm in the mood for fun, but i want more. i need more. this is not merely hormones or endorphins talking. it's something fundamentally more. in this mood i realize how lonely i am, how alone i am. i have this deep longing for the most intimate and profound of connections, a longing that, in my mid 40's, i'm afraid i will never fulfill. so yeah, maybe i'll get to fool around with some guys and it will be fun and all, but that joy will pass and i will be left in the end with nothing. and that's what i will live with and die with, nothing. what the fuck is wrong with me?