You are not a failure
It is an incredibly scary and difficult time to parent teens.
I have had my struggles with dd which I am hoping she is now starting to come out the other side of, her dad sodding off completely out of her life just as she was entering her teens and coming to terms with having a lifelong disability which may mean she's in a wheelchair by 50, the "daddy issues" meaning she chose some very dodgy boyfriends, school were shit and no support at all and indeed made her life harder than it needed to be resulting in her leaving earlier than I'd have liked, issues with alcohol (she wasn't probably even drinking much but it's a trigger for me and it meant she was putting herself at risk of falls etc which is a problem with her disability anyway) and many many arguments about all the usual teen stuff - being a slob (she's still a slob but doesn't live with me now so I don't have to deal with it!
), coming and going all hours and me worried sick, eating me out of house and home! Lacking direction when she first left school...
It's bloody hard!
She also had her share of mh issues, she mainly struggles with severe shyness/social anxiety to the point she had a stutter for some years. She also has panic attacks if she feels "trapped" in a social situation she can't see her way out of.
First - give yourself a break. You and your family have a LOT going on and it's understandable to feel overwhelmed!
Second - reach out for help! You don't have to do this alone. It isn't easy to obtain help unfortunately so I'd advise being stubborn and tenacious! Hopefully in your case the school will help you do this, also your gp and if necessary ss (they are not child stealing monsters! They are very experienced in supporting families with these kind of issues) all of these avenues will hopefully help you access support.
Check out if there are local parenting classes aimed at parents of teens (it's NOT a criticism of your parenting but sometimes new ideas and approaches are useful)
Talk to others - I have been very fortunate to have a lovely friend I've been able to be very honest with who has shared her own experiences and advised me. Hers are a bit ahead of mine.
Even my mum (with whom I have a complicated relationship) has been a great sounding board and supporter and reassured me certain things are just part of this stage of parenting.
Post on here - use a name change, change certain details to avoid "outing" but mn can be truly amazing for this stuff.
Do some reading - I gleaned from here ideas for reading material which prove useful if only to know it wasn't just me dealing with a child I no longer recognised!
Have faith - I know that seems trite and stupid at the moment but honestly, somehow they do come through the other side! My dd is back studying, hardly drinks (seriously I am actually grateful the bars and clubs have hardly been open this year!), has part time jobs (plural) and is staying with family while studying and helping them out where she can. She talks to me nearly every day and I feel like I have my dd back after a few very difficult years.
If someone had told me even a year ago I'd be feeling this way I'd have said they were talking shite! Total turnaround!
You will get through this 