I don't think he's the sort of person who would say "I love you" (impulsively or not) if he didn't mean it.

I hope it isn't him freaking out, but more of him finding it hard to express the depth of care he has for you. I've definitely downplayed my expressions of care to people, especially if I fear they'll think I'm too warm / they've expressed discomfort about the degree of care I express towards them.

My auto-correct needs to stop suggesting "HR" lol