What should I do, I kind of want him to be mine but he's with her and talking to me?

So me and this guy, we've been talking nonstop and talk on the phone for hours until the morning and he has a girlfriend and it didn't really bother me at first but now it's getting pretty serious and I'm not sure I'm okay with being the other girl. He liked me in the beginning of the year but I had just met him and didn't think that much of it. But now that I'm starting to really like this boy, we finally talked last night about how wrong it is what we're doing. He said that he's afraid that karma will come out and destroy his life but he doesn't know what draws him to me, he said my beauty and coolness. I said that sometimes, I feel wrong doing it but sometimes, in the moment, it's okay then after, I'm like WTF. He said he feels the same way but he doesn't really wanna stop talking. Then, today, we were texting before school and then after school , he usually texts' me and he didn't, I'm not sure if he's with her or if he's with his friends or just ignoring me now . I just don't know .