problem when i try to click an item

When ever I try to click on an item it wont work but when I click and hold down and move my mouse it works. And this is very annoying for PvP because I cant shift click pots into my inventory but have to click and hold and let go for it to get in my inventory. it started about 1 week ago and I was confused and couldn't do anything, so I hope you can help me with it. Thank you <3