Why does the guy feel really bad and sorry after we had sex? (Guys, please I need some advice!)?

I'm 17, and the guy is 22. We met at a party and we've made out before.
Yesterday, he asked me to hang out with him so he drove 40 mins to pick me up.
Then, we drove to his place and rented two movies. It wasn't really a date but he paid for my food, but I mean it was subway and mcdonalds..

Everything was going great; we were laughing and things weren't awkward.
Then, we had sex.
He came and then put another condom on. It was the wrong side so he flipped it over and continued to use it. I think there was *** on the side that touched me. But at that time, we both didn't pay much attention to it.
He finished pretty quickly and said I was the first Asian he's been with. I mean I didn't suck sex, he said he was about to *** when we 69...
Things weren't awkward after sex either. We were just cuddling and laughing.
Then, he drove me home and said he felt kinda bad because I was 17. Then, he also said today was fun and we should hang out again.

Today, he called and texted me saying how shitty and sorry he felt. I asked why he felt bad. He said he shouldn't have done it. Then, he asked me not to tell anybody.
I tried to make him feel better and said we were both responsible. I also told him I took a plan B pill just to be safe. He said yea he was thinking about that too.
I told him I felt bad for having to take the Plan B pill but I am going to forget about what happened.
He said he agrees and he'll do the same and I am a great person and have an exciting life ahead of me.

What does that even mean? We both weren't looking for a relationship, and I sorta knew we would do it so I was cool. Now him apologizing makes me feel like I did something wrong!
Can anyone explain to me what exactly happened? I'm so confused.

Guys, thanks in advance! I know the story is a bit long.