lightroom cc - photos losing quality when posted on website / social media

Hello!

(lightroom cc user)

I havent had this issue before except for with my new canon r6

Im having a nightmare so my photos are exactly how I want them to be at 100 percent in lightroom but then I export them, they look fine zoomed in preview but when I upload them to my wix site, instagram and facebook they lose the resolution. they are around 11mb, i have tried reducing them to 1080 res and then they look even worse! 

I have tried everything from resizing to re editing and cannot work it out. When I download them on my phone via dropbox they take a while to load but once theyre loaded and I zoom in they are also great!

Any help would be massssssively appreciated