This happens sometimes and is not a cause for worry at all.
Here we have provided a detailed, step-by-step guide for troubleshooting: We strongly recommend you try all techniques provided.
Technique No: 1
It could be your DNS issue. Connect VPN and test out speed by visiting following URLs from your browser:
http://18.104.22.168/ (should take to google.com)
If above IP open faster for you than regular URLs e.g google.com that means you need to change your DNS as follows:
Here is a good guide for changing DNS servers on:
Windows7: DNS Changes on Windows7
MAC OS X: DNS Changes on MAC OS X
iOS: DNS Changes on iOS
Android: DNS Changes on Android
Linux: DNS Changes on Linux
Technique No: 2
Distance between your location and VPN servers' location. Greater the distance lesser will be the speed. We recommend you use our server recommendation tool for finding nearest and fastest server. You should be disconnected from VPN when using the tool Server Recommendation Tool.
If none help then you will need to adjust MTU settings.
First of all you will need to determine what is the optimal value of MTU for you: Look here:
Windows: How to change MTU value on Windows (XP, Vista, 7 and 8)
Mac: How to change MTU value on Mac
Linux: How to change MTU value on Linux