You just had a big shock and disappointment. It takes time to really internalize the First Step. You've intellectually accepted it, but it takes time to absorb and really, really accept.
Give yourself time. Keep reading and posting. Read some of the Al-Anon literature every day. I think we all are more likely to get disturbing thoughts at night because our bodies and minds are shutting down. Try to let the thoughts pass through your brain without inviting them to sit down and make themselves at home.
It will get better, but it doesn't happen overnight. It's a process.