I can't stop being insecure about my relationship: help!?

I'm a 20 years old female and my boyfriend is 23. We lives 45 minutes apart and I'm his first real girlfriend (took his virginity and everything). We have been a couple for a little over a year. I care about him so much and am so in love. He claims to feel the same way. However, I for some reason am so worried that he is going to fall out of love with me and I constantly obsessively think about it. I always ask him if he's mad at me and he always says no and that I'm just being silly. Also, right now he is going through a lot of stress (car breaking down, family issues, school, work, etc. A LOT). I miss him a lot. Tonight he didn;t call me to say goodnight (like we usually do) and he said it's late. I understand because he's just started a new sleeping regimen. But the last thing he said is "You know I love you...I'll call you tomorrow." But I just CAN'T stop being so sensitive. I don't want this to ruin our relationship. Please help!