Idk what to say

This guy took me out last night and I just wasn’t feeling it. We were hanging out for a bit after and he kissed me 😳 I was like oohh shit lol it was so unexpected. Now he’s asking me to be his girlfriend and I’m like 🤔 we’ve only been talking 5 days. How do I let him down gently? He thinks it’s because he’s shorter than me or because he has a heavy limp when he walks. I just am not that into him and I feel bad but it’s my feelings 🤷‍♀️