PT10 won't install

I have a MacBook w/ Yosemite OS. I am running ProTools 11 on it…I upgraded from PT8. None of my 32 bit plug-ins work on PT11, so I’d like to install PT10. I tried installing PT10 and it wouldn’t work. Do I have to uninstall PT11 first? Or is there any advice anyone can give me? Maybe PT8 is still on my computer somehow? I dunno what to do, but, I just want to be able to use my Ozone 4 and Maxim again. Please help!!!!?? :)