18f gone away to college from 19m

So this fall me 18f and my bf of 2 years 19m started college but go to different colleges in our state. It started off great texting everyday and at least one call every night and him coming to visit on the weekends. However this last month things have been rough. We don't talk on the phone everyday anymore and when he does text he seems distant. He also hasn't come to visit me in weeks he just keeps saying he has to study... any advice? I've tried to bring it up but he just gets defensive.... should I press the issue or just go visit him this weekend?