Just want to add my own from my teens. Might help, and will feel good to get it out!
A few very early red flags - I was just 15, he was 18, early declarations of love, extreme over-reaction to me not responding the 'right way'. Ie, he was trying to impress me with some sciencey speak, and I corrected him - he shouted, insulted me, and then even cried, until I backtracked and said I was probably wrong. (I wasn't)
He would always say he was so intelligent and I wasn't. He made me feel so thick, when I really, really wasn't.
He mocked my hobby relentlessly, until in the end I gave it up.
He installed a keytracker type spyware thing on his younger step-sister's pc. I am so so outraged on her behalf now.
He bullied me into eating ridiculous amounts of chocolate. Sounds so stupid now, but he really laid on the threats. I truely felt I had no choice.
There was an incident with his father once. It was awful. His step-sister came running up to his room screaming for help, saying his dad was beating up her mum. She was so so distraght. He (boyfriend) just sat there, on his stupid computer, and told her to mind her own business. She was sobbing and was terrified her mum would be killed. I went downstairs with her and saw her 10 year old brother hitting the dad, who was hitting the mum. They stopped when they saw me and the dad stormed off. Those poor poor children. I was shaking when I went back upstairs to boyfriend's room. He had a big grin on his face and told me he'd just won some computer game. Like nothing had happened.
There was a horrible embarrassing sexual incident where he was pretending something I was doing to him was arousing, (it was a weird thing!) And then he started laughing and it was all 'just a joke'. But I was really humiliated!
He made a website called something like lardyDell28.com. To imply I was fat. It wasn't even secret. He was really proud of it and showed everyone! It had photos of me, and of very overweight women with my face imposed on top.
I got pregnant aged 16. It was 'my problem". He accepted no responsibility. Wouldn't come with me to arrange abortion. The people there would 'judge him unfairly'. I felt very uneasy about having an abortion, but equally uneasy about having his child. In the end I miscarried. Started bleeding about 20 minutes before my GCSE maths exam. He hung up on me when I phoned him crying, not knowing what to do. Should I do exam? Go to hospital? I sat the fucking exam. Got a B. Then I WALKED the 4 miles to the hospital because I had no money for a bus or taxi and he wouldn't give me any. Anyway, there were complcations and I ended up with surgery and a 10 day hospital stay. He didn't visit once. Then on the day after I was discharged, and under strict instruction not to lift anything heavy, he made me carry a large speaker up the stairs.
He videoed us having sex without my knowledge. When I was 15.
He cheated on me a few times.
Physical violence was beginning to appear. Pushes, prods. Flicks. Fucking flicks!! All the time. And they really hurt.
And then, we split up. He actually left me. I cannot believe the escape I had. I would never have dared leave him. So they are my 'red flags'. Writing it down makes it so clear how things escalated. Now for the horrifying behaviour the flags led to...
A few weeks after dumping me he broke into my house, trashed my room, and stole back gifts he had given me.
A few months later we were at the same party. He sexually assaulted me, very violently. He trapped me in the room afterwards and then started talking about how terrible he felt. Not for me, for his new girlfriend. I had made him 'cheat on her' apparently. He took out a knife and began running it over his wrist, saying he would kill himself. I was trying to comfort him, ffs! After what he had just done to me! Then he stopped, laughed, and said "why would I kill myself? It's your fault'. And then he came at me with the knife. I escaped with minor injuries luckily, but was absolutely terrified.
I just can't believe I went through all that aged 15/16. The relationship lasted just over 18 months. I am so so so thankful I miscarried the baby. To be tied to him for life would have been just awful. And I am so thankful he dumped me! Kindest thing he ever did. After the assault I moved to a new city. Literally the next week. I lost pretty much all my friends. I had to start everything again. School, jobs, house. (I was already not living with my parents). Even silly things like a new email, new phone number. I even took my mum's maiden name as my surname. I was terrified he would find me.
Over 10 years later, I'm married, nice husband, nice house, nice kids (one dead kid though - it seems not all my bad karma was spent back then), I don't even think about that horrible boyfriend often. But my God, the thought of what could have been will haunt me for a long time.
I am so thankful he only took 18 months of my life.