Sounds like you have a HDD on its way out. Assuming you start a program like MS Word or Pages, once the program loads, does it operate normally if you just try to start typing something? And then if you were to try and save your document, does it take an unusually long amount of time for the save dialog box to show up?
If you're answering yes to these, then you almost certainly have a HDD on its way out, and if you haven't done so recently, make sure you back everything up while you still can. Then replace the drive and reinstall the OS.
If you're answering no to most of this, then you probably have some program sucking up a lot of CPU time for no good reason. Use Activity Monitor to track it down and kill it, then check the login items section of the Users area of System Preferences for any references to programs you may have deleted recently or that share the name of the process you found to be using too much CPU time. Make sure those are not running at login.
Also, for the record, those cache cleaning programs are on my list of what I call snake oil scams. They are specialty tools that get marketed as some kind of general purpose maintenance type program. It's probably too late to get a refund on the program you already bought, but in the future, any program that makes rather fantastical claims about how it will improve the performance of your computer, or fix this huge laundry list of problems, is a snake oil scam program. Programs consume resources on your computer, so claiming that they can improve performance is something of an oxymoron, and pretty much universally in life, the more ails something claims to cure, the more less likely it is to do anything at all useful. I don't care if it's some miracle cleaning solution on an infomercial, a political candidate, a software program, or anything in between. The more grandiose the claims, the more you should figure they're full of ****.
Recently, Finder has become extremely slow. I've booted from my install disk and run Repair Permissions. I've also purchased cache cleaning software and done a full scan and clean.