AITAH for threatening to tell my mum a secret my dad has been blackmailing me into keeping?

In the summer, I went on holiday with my dad and accidentally found a large number of messages on his computer. From these messages, I discovered that he was in a relationship with another woman. My parents were, and still are married. It later came out that they’ve been in an open marriage for the past three years because they don’t want to divorce. My mum doesn’t work and relies on my dad financially, and they both agreed they’re not romantically compatible anymore.
However, I discovered a lot from these messages. My dad had given his girlfriend at the time over £15,000 for her studies, weekly groceries, clothes, jewellery, spa treatments, holidays, and so on. This shocked me because my dad constantly tells me that money is “extremely tight” and regularly refuses to give me money for anything at all.
I also knew that if my mum found out about this, she would completely lose it and likely do something impulsive out of anger, which would cause anarchy. On top of that, I had been dealing with serious health issues in the months before and needed my dad’s support because I had no one else. I do not have a good relationship with my mum, she was extremely emotionally abusive to me growing up, and I no longer live with her. Seeing that my dad had prioritised a short term relationship over me and our family in so many other ways honestly broke my heart. He had been lying about his “work trips”, being “too“ occupied with work to take me to my hospital appointments, but in reality most of the time he was at some hotel with his girl friend.
Last night, things escalated badly. My dad and I got into a huge argument because he threatened to deliberately create a hostile environment at home and expose me to as many psychological triggers as possible if I didn’t do exactly what he wanted. In response, I threatened to tell my mum about the £14,000 he gave his ex. That’s when he completely lost it.
He told me that if I ever threatened him with that again, or if I told anyone, he would kick me out. I’m 16, turning 17 in two weeks, and I absolutely cannot afford for that to happen. I live only with my dad, and I know for a fact my mum would never let me live with her.
He became extremely aggressive: screaming, swearing, insulting me, and at one point I genuinely thought he was going to hit me. He has been physically violent before, which he weaponised frequently to shut me down. He then said, “I’m going to tell your mum myself tomorrow. I won’t let you have this power over me.”
But this was never about power. It’s about the fact that it’s morally wrong to force your child to keep such a massive secret. And this isn’t the only one, there are many others, including when he made me take his epilepsy medication (epilim) without medical advice because he thought it would help to “emotionally regulate me”. I ended up with valproate poisoning, and when I was in hospital, my dad forced me to lie to the doctors to save his ass. I’m exhausted by the secrecy, lies, and blackmail, especially since he threatened me first.
Today, I haven’t left my room at all, not even to go to the bathroom or get a drink, because I’m genuinely scared to see him.
So, AITAH?
Facebook
X.com
LinkedIn
Instagram
Pinterest
More