I'm confused

So I was making out with this guy that I like and we both like each other and things got intense fast and I got on top of him n then I just started touching him down there but he was still soft and we had been making out for like 30mins already . So I don't get it ? Did I do something wrong? Why wasn't he hard already ? With my ex he got hard as soon as we would be making out for like a shorter time too idk