I too had symptoms similar to yourself starting at age 15. I'm 35 now and believe that i had hormonal imbalances way back then that i have not treated until now.
Before my first period i vomited, blacked out, and became hypothermic!
My symptoms of mood swings, crying spells, anger moods...skin rashes, acne, constipation, allergies...i wanted to end it all way back then. Things seemed so hopeless to me too.
Through the years i focused on diet, which got me so far with helping with digestive symptoms and acne, but the mood swings, and all the other symptoms remained and got worse.
Try to be kind to yourself. Get as much rest as you need...you say you are exhausted...sleep as much as you need to...slow your life down as much as is possible so you can take a step back and heal.
I had to do this last year as i crashed after years of driving myself into the ground. I had always said i'm never going to stop living life until 'the gods' literally stop me from being able to walk. So that's what they did. I had no strength in my legs, couldn't care for my family, animals...couldn't think, i became a complete wreck within months. I rehomed animals...stopped toxic relationships and friendships...basically stopped all the things that made my life super busy.
I slept for 9 months. Food, drink, sleep. I mentally let go of caring about anything. I was responsible for so much before crashing, i took everything on. So my best advice would be to try to 'cut out' of life all the stuff that fills your life up and causes stress.
I would seriously recommend a hormone panel so you know what your levels are at. canaryclub.com (or .org?) offer the cheapest saliva tests online - they post you out a kit...they offer this to europeans too. Cortisol x4, DHEA, estrogens, testosterone, progesterone is one panel they do that could really show any imbalances.
I'm sorry your parents are not taking this seriously. Mine didn't too when i was 15. I left home! Not something i would recommend. Parents are difficult to talk to at the best of times but if you could ask them to talk...and ask for them to help pay for the saliva tests, the results should speak for themselves.
Try to find the strength to talk openly with them to help you. I never told my parents i was suicidal. If i had been open about the hopeless grief i was experiencing i know they would have listened. I was too scared to share with anyone at the time. It took much more strength to support myself financially at 15, pay for my own place etc. If i had used that strength to share with my parents i may have not needed to suffer for 20 more years with health problems.
I know we're all different and symptoms have many causes, but in this world of estrogenic, goitregenic foods...hormone imbalances are affecting so many people and they often show up as 'psychological symptoms', which is the downfall of many people's long road to never recovering while on psych meds because the true cause has never been looked for.
It's only my opinion that out of all tests to be carried out, i would opt for hormones to be checked out. Others have different ideas. I spent years doing cleanses, detoxes and fasts, which helped digestion mainly, but didn't change other symptoms. Cleansing won't drastically change hugely imbalanced hormone levels.
I wish i could be of more help...i really do know the hopeless lost feeling well...and i empathise with you. I tell myself when feeling that way that things will change, nothing stays the same. Please hold on to the strength you have to try to find answers, the strength which brought you here to ask for help...many here experience what you are going through so you have a place to talk freely and express yourself.