i keep trying to update to latest version but everytime it just re-downloads 7.6.33 version from website
This is a bug / misconfiguration in the 7.6.33 release; it is reporting the availability of an updated BOINC client when it shouldn't be! We are hoping to fix it without any action being required on your part and those update notifications would go away.
As Adam says, though, if you want to keep up with the latest version of BOINC, you are free to do that. We don't test it with Charity Engine, so it would be something of a "beta testing" approach on your part, but it's unlikely you will have any trouble.