Advice plz: getting "serious"

So I met this guy when I was 12, he was 13. Now we are 24 and 25. We started casually dating at 17, we would go on a few dates and drift off as life got busier and more complicated as we were both in on & off-again relationships with other ppl and he moved to another province for a year to work. He's always been very respectful and kind. Now we recently reconnected after both being single for a long time (a year for him, I just casually date now since my last relationship three years ago). I had lost my election at our school and he suggested we celebrate that I tried anyway, so we did and he asked me to be his girlfriend, one thing led to another and after 7 years we finally had sex. I really enjoyed it, everything was perfect the next day we went to my favorite cafe (his treat) and spent the day together watching movies at my apartment and going to a diner (my treat). We ended up having a fight after a couple weeks and I stopped talking to him, assuming he didn't want to be with me anymore. Two weeks later he reached out to me and apologized online and on the phone for half an hour, that night he was taking his sister to the airport and asked me if he could pick me up on his way home. I said yes and we ended up talking and cuddling so I felt better because it seems like he doesn't just say things for sex you know? Anyway, q couple weeks ago he invited me to drink with him and his friends and I was hesitant because I have been drugged by someone at a party before when I was with a friend at their friends house party but I didn't want to tell him that, I ended up going anyway and it went really well. We played beer pong and drinking games all night, we actually make a good team and his friends were super nice - too nice. We were walking to his apartment and he started getting all insecure, saying I was being so friendly and flirty and I tried to reassure him I was only interested in being with him, I wasn't touching his friends, giving out my number or anything while we were talking and he was still really upset. He said he wants me to be serious about being serious. Idk what that means? Since then he's been acting really quiet and shy, I think he might be embarrassed about getting emotional but I don't know what to say or if I should just leave it alone. I don't want to further embarrass him by bringing it up. I just find it hard to get into emotional conversations because I'm not used to having someone really care about me enough to want a deep connection, I tend to push people away or keep them at a distance.