<human>: Can you provide a brief rundown of the text in within 3 sentences?

My boyfriend and I have been dating for 4 years and everything is wonderful. We have a lot in common and I feel like we're both on an even keel and are good at handling our problems. There is just one problem that really seems unhandle-able, his sleeping disorder.
 

He is physically unable to wake up before 4 or 5 pm, and sometimes will sleep for 24 hours straight. He has sought treatment and was turned away from several clinics because they just could not help him, though they suspect Delayed Sleep Phase Syndrome or some other circadian rhythm disorder. Luckily, they were able to give him documentation to give to his work, so that is not overly affected. 

I feel very selfish making this about me, but it's beginning to make me feel VERY isolated. I have a day schedule that begins very early in the morning, so I usually go to bed fairly early in the night. We don't live together and because both of our work schedules are only able to see each other on the weekends every 2-3 weeks. This would be fine, but because of his sleep, he seems to literally drop off the face of the earth until we have plans. I have even told him, "It only feels like I'm dating someone on the weekends." 

He does try to help and I can tell when I bring it up he's left feeling awful because it's something he really can't control and would love to be rid of. So I feel uncomfortable bringing it up, but it's really affecting the relationship in my eyes. Is anyone in a relationship like this? Any advice? I really don't want to end this otherwise wonderful relationship.
<bot>: My boyfriend cannot physically wake up in the morning (he wakes up very late in the evening/night) and I'm left feeling very isolated.