Getting stuck in the obsessive loop is terrible. Been there, done that. It's a hard cycle to break, but it can happen, so don't lose hope.

Obsessing is exhausting, and exhaustion can lead to obsessive thoughts. See the problem here?

I probably recommend this book way too much, but there's a book titled Hope and Help for your Nerves by Dr. Claire Weekes that addresses this sort of situation exactly. It's an old book, but easily one of the best. She explains the physiological reasons that the pattern happens, and how to break it. If you're interested, you can do the "look inside" thing at Amazon to see if it might apply to your situation.

The other thing I found very helpful when my anxiety/obsessing was at it's worst were some of the exercises at the dbt self help .com website. The programs are designed for people with BPD, but they are very helpful for lots of other situations as well. The section on distress tolerance, radical acceptance, and turning the mind is pretty good for changing thought patterns.

It can get better. Keep looking for your answers.