I recall replying to you introductory post.
You mentioned not knowing the cause of depersonalization. I'm not a mental health professional. So I can't give you a professional opinion on that. But my understanding is that, while the causes are to some extent not known, depersonalization is sometimes considered to be related to anxiety.
You wrote that your school counselor said you have "suppressed emotions", which you said you don't feel is true. You just feel very sad & you asked how you'd know if you have suppressed emotions & how do you help it. I believe the primary way people typically figure out these sorts of things is by talking through what's going on with them... with a family member, a counselor or mental health therapist.
It is possible, I would suppose, that the sadness you are feeling is simply due to your age. One's teenage years can be a rollercoaster of emotions, as I'm sure you realize. But it is also possible there are some things going on with you, & in your life, that are causing the sadness you feel... perhaps things you don't even realize are having the effect they're having. Talking through what you are feeling is the way to figure out what's going on. It would be great if your doctor could just take an x-ray & tell you why you feel sad & depersonalized. But emotions don't work that way. We have to think about them, talk about them with knowledgeable people, & do other things to help us figure out what's going on & what to do about it.
Here are links to 5 articles from Psych Central's archives. The first 4 are on the subject of depersonalization. (The fourth is actually targeted at parents of kids & teens.) The fifth offers tips for coping with your emotions when you're a teenager:
10 Simple Ways to Relieve Depersonalization
Depersonalization: A Strange Mental Illness Captured in Films, Music & Celebrity Confessions
Is Depersonalization Disorder a Form of Enlightenment?
Depersonalization in Anxious Kids
Techniques for Teens: How to Cope with Your Emotions
My best wishes to you...
P.S. Here's a link to a YouTube video by family therapist, Kati Morton, on the subject of depersonalization / derealization that may be of some interest. If you're not familiar with Kati's YouTube channel you might find it to be a helpful on-line resource:
https://youtu.be/H564Dmsksz0