The end of a relationship is like going through withdrawal. Actually, there are pretty good studies showing that a breakup is physically a withdrawal process. When we are in love, our body produces chemicals that act like morphine in the body. They are called endorphins. When we go through a breakup, our entire body responds. People with arthritis often find that it improves because their immune system has partially shut down due to the grief. People either gain or lose 10-15% of their body weight. I lost 15 lbs after my last breakup.
This is obviously your first love, and it feels like you're going to hurt this way forever. It takes a long time, but you do eventually feel better. To get through something like this, you have to keep reminding yourself that it will get better.
The busier you can stay, the better. Exercise can help your body and emotions return to something like normal. After my last breakup, I would go out and run for 30-40 minutes straight, after going to the gym for 90 minutes. I literally drove myself to exhaustion so I had to sleep.
You need to reach out to your friends in this situation. YOu may need to even ask them to help keep you busy. For the time being, it's probably healthier to put the mementos of your relationship away. Don't throw them away, because the day will come when they don't hold the pain they hold now. But you need to stop reopening the wound.
This will get better. And you have to keep telling yourself that. The bad days will get fewer and the pain will get less intense as you move through the process.
I don't know anyone who has reached adulthood without at least one broken heart. I've had three in my 45 years. It's terrible, but you do get through it.