load time issues

About a month ago, home pg of my blog suddenly began loading very slowly. Slow-down not associated with any obvious thing — no new plug-ins, no sudden increase in use of photos (in fact, I’ve really cut back on them — but no improvement). My readers are complaining, and according to InternetSupervision.com (which pings site from servers all over the world to test load time), load times have often been in excess of 20 seconds. My tech-savvy brother says the database is bogging down (sorry… he lost me in the details), but we aren’t entirely sure how to optimize (I’ve sent him the very few ideas I found on the WP forums… he’s also suggested WP-Cache 2.0, though another forum suggested that isn’t the best solution either. Godaddy is my host, and I’d like to know what others think of them… how likely is this to be simply a hosting problem? Thanks mucho in advance for any other ideas… if I can’t understand them, my brother might! ??