Delay in updating changes?

[Chromama]

I'm having a hell of a time customizing my website at the moment - I'll make a change, then hit save, and then view site, and it still shows the last version. This is most noticeable when I'm fiddling with the theme, but it isn't specific to any one theme...so switching between themes (with no extra customizing) will show the old theme, even then I'm certain I have uploaded/activated the new one. Eventually it will catch up with itself but the delay isn't seconds, it's minutes, sometimes hours at a time...when I go into the Dashboard and open up Editor, or Themes, it clearly shows one theme installed but then when I preview the site, changes don't appear to have 'caught'.

It's maddening, especially when I'm fine-tweaking things like the nav bar...I need to be able to see each change as it happens, naturally, to know whether or not I'm in the right spot! I can't account for the weirdness, can anyone help me out? Could it be a computer thing? (I'm working on an old laptop)...all the other work I do on this dinosaur seems to shuffle along fine, but this delay when fiddling with my blog is a major headache