Remus worries. A lot. He worries in a way that would probably be considered uncharacteristic for a teenaged boy, but worry seems to be oblivious to this and follows Remus around everywhere he goes. Worry follows Remus around by day and by night, and Remus can never quite get it to go away.
Remus worries about the scars that run across various parts of his body. He worries about what people will say when they see them, namely the three jagged scars that run across his face. He, James, Sirius, and Peter know that these particular scars were self-inflicted, that he had clawed himself across the face once during the full moon. Remus worries about the stories that he will have to think up when another scar appears on a place unable to be covered by clothing. Remus worries about what people will think, what they will say, if they see past his lies and discover the truth.
Remus worries about what will happen to him after Hogwarts. He knows good and well the prejudices people have against werewolves. He's surprised that he was admitted to Hogwarts, actually. The fact that he has friends—friends who know he's a werewolf and even became Animagi for him—is so lucky…Remus often thinks that he's dreaming and will wake up anytime now.
As if worrying about life after Hogwarts isn't enough, Remus worries about his classes. Oh, he's fabulous at almost all of them, that's for sure, but that's because he works hard. Sirius and James would get by just as well as he does if the prats just studied every once and a while. Then there's Potions, which Remus is horrendous at and secretly worships the ground Lily Evans walks on for tutoring him in it. Potions makes Remus worry a whole lot; so much so that Sirius insists that he's going to have gray hair before the age of forty.
These worries, about his scars, life after Hogwarts, and his classes, are generally known or assumed by Remus's friends and others who know him. A worry that Remus is quite sure is only known by himself is about his and Sirius's relationship.
Sirius is too good for him. Sirius is handsome, Sirius is charming, Sirius is pure blooded and rebellious and has that bad boy demeanor about him that makes people swoon over him. Sirius is Sirius and Remus is Remus. Sirius bounces around from person to person and has one-night stands. Sirius can be with anyone he wants. Sirius can be with everyone he wants. Who is Remus to come along and change this? Remus isn't desirable.
Which is exactly why Remus worries. He worries that Sirius will toss him aside like all those people before him. Those people who are much more attractive than he is, don't have a slight obsession with books, and, oh yeah, aren't werewolves. Sirius doesn't really love him like he says. Sirius is playing with him. Sirius is going to hurt him, and he should run. That's what he tells himself. That's not what he does.
Because Remus loves Sirius. He loves him more than books and libraries and interesting facts and other Moonyesque things. Remus loves Sirius so much that it hurts, and he worries that Sirius doesn't feel the same.
All of these worries whirl around in Remus's head at any given moment, even when he's asleep. They manifest into his dreams and gnaw at his unconscious self. Remus has noticed, however, that when he sleeps with Sirius, only one of his major worries eats at him.
The light skitter of fingers across his forehead is not what wakes Remus, though it is what makes him realize that he's awake. Remus does not open his eyes and does not stir. Instead, he senses.
Remus knows the way that Sirius works. He knows little things that no one else knows; that no one else pays attention to. Sirius is thinking now, and Remus wonders just what it is that has caught his thoughts at such a late hour. Suddenly, Sirius tenses, and Remus knows that Sirius's thoughts have led in a direction that he doesn't like.
"Sirius, are you awake?" Remus says, feigning ignorance, rubbing one of his eyes, and yawning. Remus knows that when Sirius starts to think about Things, it's best to not let him suffer alone, even if he is pigheaded and often unwilling to let others help him with his issues. "What're you thinking abou-" Remus doesn't have the chance to finish his sentence.
Sirius kisses him—hard—and Remus's eyes snap open. Remus doesn't have time to process anything before Sirius is saying, "I love you. I love you, I love you, I love you." And then he kisses him in a way that conveys everything that Sirius feels for him. Remus stops worrying.