Tommy has always been described as clingy. Maybe a little too clingy, as of late; unhealthily so, possessively so, even. Tommy's been through a lot; he's just a kid who's suffered under neglect, abuse, and trauma, through grief and betrayal and heartache and sufferage. He went through things he was too young to have gone through, and he experienced things no child should ever, ever have to experience. He was hurt. He was scarred. He was broken, irreparably, fractured and fragmented into a million pieces. You picked him up; you're the glue holding him together, keeping him intact. His entire life, people have left. People have abandoned him, left him to die, left him to rot. People have left him. He doesn't know if he can handle one more person leaving. No, he does know that he couldn't. He wouldn't survive if you left. You can't leave him. He'd die if you left. He'd kill himself if you left. And it’d be your fault. His blood would be on your hands, because he can't let you leave like everyone else. He can't handle being alone again.
Like history is doomed to repeat, the cycle of abuse is always doomed to continue. The abused become the abuser; hurt people hurt people. Hurt people become the very thing that hurt them all because they never want to be hurt again. He doesn't realize he's become exactly like the person who made him this way. He doesn't realize he's just like him. He doesn't realize the story's being retold, except he's the villain, this time. He's the abuser.
He didn't mean to hurt you. All he wanted was for somebody to finally stay.