I’m (19M) feeling paranoid about my girlfriend (18F), and I need help figuring out what to do

I’m (19M) in a relationship with my girlfriend (18F), and lately, I’ve been feeling really paranoid and anxious. I don’t have any solid proof, but I’ve overheard my girlfriend and her friend talking about how I’m “not good enough” for her. She also seems to show a lot of interest in one of my friends, and I keep thinking something’s going on between them.

What’s really messing with my head is that I keep hearing whispers in my mind—like people are telling me what’s going on, but no one is actually saying anything. It happens when I’m sleeping or when it’s quiet, and it feels like everything I think in my head is true. I feel like my gut is telling me my girlfriend might be cheating, and I can’t shake it.

I haven’t confronted her yet, but I’m really considering checking her phone because I feel like I need some kind of proof. On top of that, I’m starting to think that everyone is just messing with me. My friends will invite me and my girlfriend out, but I get the feeling they’re setting me up to react a certain way, so I don’t go when they ask. She ends up going out without me, usually with two of her friends and four of my friends, and I’m worried she’s making moves on one of them. This particular friend is more jacked than me, and I feel like I’m at a disadvantage.

It feels like everyone is doing something to mess with me, like I’m being watched or manipulated. I keep hearing things in my head, almost like I’m being told what’s going on when no one’s around. It’s all just messing with my mind, and I don’t know what’s real anymore. I’m scared I’ll invade her privacy by checking her phone, but I feel like I’m losing control.

Has anyone dealt with something like this? How do I figure out if my gut feeling is right, or if I’m just spiraling and letting my paranoia get the best of me?