In the Mouse Properties
Checked the "Switch primary and secondary buttons" and then unchecked it. See if its working. If not then try this.
1. Download CCleaner by Piriform (free) CCleaner - Free Download - Piriform
https://www.piriform.com/ccleaner/download
2. Start CCleaner
3. Then Tools (left hand menu)
4. Then Context Menu (top right)
5. This will populate and give you a list of shell.dll files
6. Then disabled the file: BTMSentToExt (Intel Corporation)