Really worried

My so and I (16 and 15) have been together for almost 2 months and before we started dating and until about a week ago he put in a lot of effort and always kissed me and left me notes and I always did the same for him and he told me I was beautiful all the time and now he’s leaving super short messages and stuff and just acting super weird. Yesterday he dodged my kiss and just said it was “an off day”. I don’t know if it’s about me or if there’s something going on but I don’t want to be clingy or pushy. What should I do?