I feel like my boyfriend is losing feelings.

Ja
My boyfriend and I have been together for 1 y and 1m. We were madly in love for a very long time. I still love him with all my heart, but I feel like he's starting to lose feelings for me, which scares the hell out of me. I'm only 15 and he's my first love, first kiss, and even first time. He's my everything, but idk if I'm his anymore. He doesn't seem as happy to see me anymore and he takes forever to reply to my texts. We're only allowed to text in the weekends and holidays/ breaks bc his parents are super strict and want him to focus on school and not me, which I 100% respect. Anyway, he's always grounded, which means no texting on the weekends, but when he's not grounded, he's so boring when we text. Like our conversations used to be so fun and cute but now they're short and uninteresting. I've talked to him about it and said "Are you still happy with me?" And all he said was "Yes I'm very happy" with almost no emotion. I really don't know what else to do, I'm texting him right now, and it's the same old boring conversations we always have. I try to make them fun but he never puts in any effort. He's always playing video games with his friends, and I feel like he cares more about his Kill to Death ratio than me. I'm so confused and scared that he doesn't love me anymore and idk what to do.