Hi MT. Welcome here to BB forum.
I cant answer your question directly as it involves medication and an individual with that medication. However I can describe my experience which might help.
I was initially mis diagnosed as having ADHD in 2003 at 47yo. Then in 2004 bipolar 1. The subsequent medication saw me so tired during the day many incidences occured of me drifting off the road when driving. No matter what I did I could not stay awake.
Then my relationship went south and I went off medication in 2009. Suddenly I had my alertness back. I remarried and my new wife who had known me for 25 years as a good friend, went with me to another psychiatrist and he correctly diagnosed me with bipolar 2, dysthymia, anxiety and depression. The anxiety has since disappeared.
I was given mood stabilisers and a small dose of anti depressant. What a wonder. I have since then improved every day and although very aware I'm still and always will be fragile in mental health overall, am thrilled I am much stronger. I recall those years of tiredness and snappy mood, manic periods and sadness not to mention my then girlfriend that put up with it all.
I suggest a couple of things. Seek a second opinion and dont be afraid of doing so. It's your right and it could save you a lot of heartache.
I know you are at wits end. Try to see him as desperate for your help. Dont give up, seek more help and guidance. Whatever community and medical support you can muster. Post here more often to ask questions. Read the many threads here as it is a great source of information.
Finally, your husband might well have a sleeping disorder. If so this will make him tired all the time. Ask your doctor to get him into sleep clinic for a sleep study (I've done 2) where they monitor him overnight. I was mild to moderate sleep apnea and require a CPAP unit every night. boy...do I sleep well now!!! It can also lengthen his lifespan...its that serious.
Good luck and keep us posted.
