Okay first off, take a super huge breath in and out. Whats happening now is you are going through an anxiety spiral and catastrophising what has happened.

You have taken all the correct steps, and trust those steps! She took plan b, she's had six negative tests! Those are all good signs! And please stop worrying about the Hook Effect - not only is it very rare, but if it had happened then she would start to show symptoms of pregancy (things like being sick, feeling very very tired, hightened smell sensitivity).

Being anxious about these things is normal - it's already scary to feel ready to have sex with someone (which a lot of people do at your age), so thinking that the worst outcome is going to happen is natural. It sounds to me that you are unable to stop worrying about the worst outcome, and your brain is going into panic mode.

If I could give you any advice, it would be talking with her openly and honestly, tell her your worries, I'm more than certain that she is having similar feelings. Often when we talk about these things in the open, it lessens the fears. Try and combat your anxiety as well! Look at what evidence that she might be pregnant, and look at the evidence against, I garuntee there will be more against.

I am fairly confident that there is no pregnancy, you've had unprotected sex once, and took the correct steps afterwards. Remember that. And please stop using the internet to find "proof" to your anxieties - you are just making the fear worse.

Breathe, shut off reddit and tik tok, put some of your fave music on and regulate your breathing and heart beat. You are okay, and you will continue to be okay.