Not sure if I can bring up LGBT to counsellor.

I'm not sure on the details exactly - I'm sure most counsellors aren't going to do this. I went to one-on-one counselling once when i was 16 and the counsellor wasn't allowed to even confirm to my parents that I had been there without my consent.
However, this may be an age thing so I'd check to see if anyone under 16 has had 'confidential counselling'.

 

Went to a counselor in 7th grade about self harm, and I was almost forced to tell my parents about it. The only thing that stopped him was telling him they already knew and we're trying to help me with it.

Sometimes, they legally have to- considering you're hurting yourself.

It's unlikely though.

 

Self harm is different than sexuality or gender identity. Counsellors must tell parebts or others if a kid threatens to harm themselves or someone else. And while many do it, outing a child client should technically be a breach of confidentiality. Flat out ask the counselor about their policy and bring up the story about the friend you have.

 

As you are underaged certain aspects of your counselling can be subject for discussion between your parents and any counselor, therapist, psychologist, psychiatrist, etc. But these are usually details which may warrant discussion or are of concern. If gender identity is not really related to your issues discussed with the counselor then normally this wouldn't be even mentioned between them. Some counselors would even ask if there are parts of the discussion you wouldn't want him/her to discuss with your parents. Or if you strongly feel about it you can take the initiative and tell him/her that you do not want your sexuality to be discussed outside of you two.

Threats of harm to self and others are a whole other matter. Counselors, Therapists, Psychologists, Psychiatrists, etc even Priests (at confession) are bound to inform your parents (in your case as you are a minor) regarding matters such as these.

 

What you say to them is confidential unless you're in danger of harming yourself or someone else.

Bring this up before you start the session. Ask them to explain in detail the confidentiality agreement.