Borrow or go ahead and buy Clinical Anesthesiology published by Lange and read the chapter on Pain Management ~50 pages. That should give you a decent enough background to ask insightful questions and understand what they're talking about and doing in pain clinic. Jump to other chapters to flesh out other questions which arise while you're reading that chapter.
Was gen anesthesia a lottery process for you? Or did you apply late, get unlucky? No chance of general anesthesia at all during your fourth year?
Was it offered during 3rd year?
I vote for all MD schools offering anesthesia as either a requirement or an elective that you are guaranteed to get sometime in 3rd or 4th year. 🙄