I am Lost in my head I don't know how to stop thinking about him ?

I know how difficult it is to stop thinking about this person, especially if they're dancing around in your thoughts or everything you see and hear remind you of them. But realize that your feelings are valid, it is okay to feel this way. The best thing I could suggest is to surround yourself with family, friends, or even a counselor to get the emotional support you need to get through this difficult time. You can also talk to one of our listeners on here as well! Find a hobby that you're passionate about; get creative and express yourself. Remove items or even songs that remind you of him, and possibly don't go through his social media. You'll be reminded of him more this way. I can't guarantee you can stop thinking about him instantly, sometimes with obstacles like this ...it just takes time and patience. But every time you think about him, try to stop and think when you find yourself looking at another flashback, and replace that memory with something good, like a time when someone made you laugh, or when you accomplished something. Hopefully this will help.