Hiya. Just a few quick things, the first two insultingly obvious:
1. You're still only 18. Patience, young man! Do you think you're the first guy who was ever confused and weirded out by sex in history? Who ever worried about being maybe gay or bi, or if so, what kind? About being a virgin? About feeling guilt about masturbating, all the way back to age 12? I'm not bullying or teasing, I'm just sayin' ... You're NORMAL! Sex is COMPLICATED! Relax! And ... back to the beginning ... you're still only 18!! Do you *really* think very many 18-year-old guys have sex all figured out? Wrong! Most of 'em are just fakin' it till they make it -- I guarantee it. If jacking off is what gets ya through the night, then keep doin' that. (Hey, I did! Now I'm married and sometimes I still do!)
2. We all know there's no such thing as normal. You sure aren't. Neither am I. LOSE THE OBSESSION over whether you're "supposed" to be gay/bi or when you're "supposed" to get laid or how you're "supposed" to feel. Easier said than done, I know, but trust me: You'll save yourself gallons of stomach acid. As for me, I dearly wish Wikipedia's entry on libido had existed decades ago. (Read it NOW.) I'm in my 50s now, and I angsted for years about not feeling horny "enough" according to how my friends seemed to. Well, guess what? Everyone has different levels, as it turns out! And it seems to change all the time! And, whaddya know, it's apparently like personality, of all things! It's like obsessing over how long your penis is when you're 15. Just stop it! You have a penis, and you feel sexual! You're gonna be fine!
3. Finally, major props to you for getting a therapist this early. I didn't get there until I was 25, and it was the best thing I ever did for my sexual issues. Furthermore, if you don't like how this therapist works for you, fire him or her, and get another one. Rinse, lather, and repeat, until you get a good one. Becoming happy with who you are sexually is an important part of being a healthy adult human, and you seem to sense that. It is to your great credit that you are reaching out in this respect.
Overall: DON'T WORRY. You are young, you have MUCH to learn yet, and please know that life and love -- though often challenging -- are long and winding roads of rewarding joy and happiness.
Finally ... you are a much, much better person than you think you are. Never forget that! Keep us posted on how you're doing. (I have a feeling you're gonna keep getting better and better.)