All you did was have your head turned by someone who was giving you attention, which is what you wanted. However, you were too young and immature to realise it was the wrong kind of attention, especially when sex was involved.
He's an adult and, even if he had just been dating you, he has nothing in common with someone who is still a schoolgirl. He knew what he was doing was against the law and he manipulated you into this situation because he saw you were vulnerable. There was no real love from him, no matter what you might think.
I hope you have had support to get through this, and to try and resolve the situation at home. Please don't see your mum in a bad light; she did the right thing in pushing to get this predator off the streets. Jail stops him from hurting you more, mentally or even physically, because he could have become being more controlling with you, or from raping anyone else.