Welcome, feels alone! Glad you found us.
The school nurse, or counselor, sounds like a great idea for a place to find some help. The other good source would be your family doctor when you are home for a visit. Any of these professionals would/should take your concerns seriously and offer useful suggestions. They would also keep your information confidential, which is important.
I'm sorry your mom didn't take you more seriously. She is right in that changing body chemicals/hormones can wreck havoc during teenage years and cause lots of different moods - but you asked for help and didn't get it. Perhaps if you could let her know how much you were hurting she would not brush you off so quickly.
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