Safari is very slow in latest OS on MacBook Pro

Hello,

during the last few weeks I have been very frustrated with my Safari connection. The websites take some good 5 minutes to open completely and I am trying to open YouTube as I write. What it concerns me the most is that my internet connection in my PS4, iPad (device which I am using right now), iPhone and my desktop (not Apple product) is perfect and also my Macbook Pro Safari will work just fine only if I open it in a private window. I have deleted the history and the cache and all those things in Preferences, at the beginning it seemed like if the problem was solved bit just a few minutes ago I was trying to log in into my Youtube account and it is still loading. Is it time for me to upgrade to a newer version of Apple laptop? These are my device's characteristics:

OS X Yosemite Version 10.10.3

MacBook Pro (13-inch, Mid 2009)

Processor 2.53 GHz Intel Core 2 Duo

Memory 8 GB 1333 MHz DDR3

Graphics NVIDIA GeForce 9400M 256 MB

Thanks for your attention and time.