Six weeks in I stopped being able to sleep and after a week got ambien from my doctor. I didn't use it every night, but was glad to be able to shut my brain down and get some quasi-rest every other night or a few times a week. Definitely an option.
When I had my second DDay a month later and exited limbo my ability to sleep came back immediately after my fearing that perhaps I would never re-learn how to sleep. That's something to keep in mind too--that if you can make a (relatively clean) break, your obsessive thoughts/anxiety may recede.