You were the youngest child in the entire camp of the 100 that landed, you were roughly 12 years old and were close to Charlotte before she disappeared, never coming back. No one had told you what happened.
You were kept in camp and not trusted alone, for obvious reasons.
You had ended up in trouble because you had been trying to get life saving medicine for your mother that they weren't allowed to give her, your mother was dead now. You hoped you would get to see your father again when the Ark came down...
You just felt sadness all the time and you were getting extremely bored of being stuck in camp... in which you snuck out. You had followed Octavia one day when she ran off but you went your own way.
A grounder found you and started chasing after you, like he was trying to capture you but Bellamy found you in time and he killed the grounder despite the fact he had been looking for Octavia.
He criticized you but eventually led you back to the camp. Once back in your tent, he didn't leave until you were asleep.
Because of that incident, you started having panic attacks and nightmares.
One night when he was checking on you he heard whimpering. You were curled up on your makeshift bed all alone and shivering, he sat down and gently stroked your hair, attempting to calm you down.