what do you think?

I need some advice and to see an outside perspective. I've been "talking" to this guy every single day since June (genuinely we have texted every day), after we met through work at a summer job. At first we were talking just to hook up, since he's 25, lives in Cali, and I'm 18, and go to college in Washington after the summer ended. Well, we started to catch feelings for each other, per the usual issue. At one point we were nearly drunk laying together and he told me if circumstances were different he'd marry me. Since I went to college we have continued talking, flirting, all of that, and he even came down to visit me for a weekend. We aren't exclusive, he encourages me to have fun in college and not be bound down to him. 
The problem is, I truly like this dude, but he doesn't show his emotions the way I'm used to. I'm very affectionate and I want to compliment him all the time, and I need some sign of affection or intimacy at least once a day. Well, he is not the kind of guy to express his feelings, and he doesn't understand why I need that affectionate reassurance. I think it's because of the age difference; I'm used to my peers and love interests texting all the time and being affectionate over text like it's not a big deal,but I'm sure it wasn't like that for him growing up. 
I have an actual issue where I feel like he doesn't like or care for me when he doesn't express it directly (like saying "I miss you" "can't wait to see you" "you look good today" etc.). I end up starting arguments because I feel unappreciated. I have talked to him about this many times and nothing changes. I just would love to hear other opinions; do you think this is just how he is? Should I worry? Do I have nothing to worry about? 
Thank you so much 💕