Mouse clicks

I have had this issue with 3 different mice now and im not sure whats causing it. Randomly when using my PC, the right click context menu will just pop up and if I ever try click anything normally, the right click menu comes up. I dont even have to be using my mouse, I can be hands off...

I can get: i5 7600 8gb ram 600 watt power tower cooler motherboard h270f asus For around €300 (not new) I got an old aurora r3 case with sdd, usb etc in it Can I use the cpu and motherboard etc in it. And for the time being playing overwatch, wow, lotro on medium till I can afford a good gpu...