Help my 15 nearly 16yr old son is uncontrollable

Help or advice please. On mobile apologies. My son has been acting rage anger issues and wild mood swings for 2 years now. We lost my mother last year who was his go to person as she was mine. But he's started to spiral. He's yelling and hateful and nasty for days. Then remorseful for about a day. Then back again. It's made me ill. Made his father (not together and doesn't live with us) ill too. Me with a blood pressure issue, it killed my mother so I beg him to stop. He does have a bereavement therapist and school help. But he won't get up to go. I have to spend hours begging him to get up and go, nearlylost my job, the only income, becauseof this. My own grief has had to be put away because he is acting so wild. If we threaten to take away phone etc he threatened self harm. I'm at my wits end. Doctors said school need to refer, school say need doctors. My son needs help. Uk. Advice please x