It is called Non-24-hour sleep–wake disorder [1], and is very common in blind people. I have it (though not blind). The Wikipedia article suggests some treatments. It's impossible to fix in my experience by forcing myself into a consistent cycle; I'll just grow more and more tired over time until I simply fail to wake to alarm.

[1] https://en.wikipedia.org/wiki/Non-24-hour_sleep%E2%80%93wake...