[Help] Boyfriend is going out of town for months and I don't know how I'm going to make it

I met my boyfriend online, and he ended up coming down to visit me, and has been staying with me for 7 months. He's planning on going home soon though (he's having laparoscopic hernia repair surgery) and I don't know how I'm going to cope without him here.

I have a lot (read: crippling) anxiety about him, about something bad happening to him. It was really bad before he came to visit, but I feel like I may have lost my ability to deal with my anxiety now, since he's been here so long, giving me a nice vacation from my anxiety.

I feel like I have so much to worry about. What if his train derails on the way home? What if I can't afford to visit him when he has surgery and something goes wrong? What if he gets in a car accident and dies? What if this and that? Not being able to "control" every situation is driving me crazy with anxiety.

I can't afford a therapist (not even with a sliding scale payment) and medication doesn't help me, so I'm pretty much on my own. How can I reassure myself that he's not going to die in his sleep, get t-boned every time he leaves the house, or have an aneurysm while he brushes his teeth in the morning? I'm desperate for advice!