I don't understand why being gay or being a lesbian is a sin

I am having a mental breakdown. After reading the Bible, I was shocked at this verse. Now just to be clear: I am not gay. I am a straight teen who thinks it's unfair that gay men and lesbians get attacked by Christians. Now the verse that I'm talking about is "You shall not lie with a male as with a woman; it is an abomination." Now when I read this, I interpreted it as you shall not have a threesome as a man, with a another man and with a woman. So I promised to myself that I would never have a threesome. But when I learned the truth, I was heartbroken. I see people turning 'straight' for God but my question is are they changing for themselves or are they changing for God? Because if they are, it just messes me up. I started thinking "Why God? Why can't the same-sex be in a relationship?" I started to feel sick in my stomach. It gets even worse when I heard that the Bible doesn't care what you think or what you interpret. And I started thinking if the Bible doesn't care what I think, then does that mean God doesn't care what I think? And if he does, then what love is he giving me if he doesn't care what I think! I'm just conflicted. I love God and Jesus and I want to follow them both, but all of this just make it so hard.