My [18F] Long Distance Boyfriend [19M] of Roughly Two Years Is Not Responding

8 days ago my boyfriend went MIA. No calls, texts, Skype messages, nothing.

I can confirm he didn't die because his Mom saw him at work last Wednesday (He moved out, has his own apartment and car, but shares a shift with his parents at Amazon on Wednesdays).

We live 8 hours apart and I am a full-time college student and thyroid cancer patient so driving to see him is not a viable option.

He has broken up with me before (last year for two months) but he made his intention very clear at the time. There was none of this ghosting bullshit.

He does not have internet access in his apartment and our only means of communication is by phone/snail-mail. Thus, I've sent a letter (last Thursday) to try and get some answers, but I have no way of knowing if it will reach him.

This is really starting to upset me. Do you think it's just his phone or something more? What should I do? Wait and see what happens? Or do you guys have another suggestion?

I feel I should add that we literally Skyped the day before he disappeared and everything seemed absolutely fine. There was no indication that this was planned, but still....

tl;dr: LD BF gone ghosty. I'm upset. What do?