Pictures dont show up in any social media

i recently notice that my featured images where not being shown by facebook after i posted them on WordPress.So i did some research and was told to use different pluggins . which didnt work so i went bare bones and turned off all the pluggins. It still did it so i look further and it turns out that it was the links that wordpress put up they didnt match so it didnt show the picture. WordPress would post a certain size like 100×100.jpg at the end of the real link to the picture. What i want to know is how to fix this i want my pictures to show on facebook. Oh yeah when i do a copy paste into a post with a picture in a post it does appear in the social media posts. it only doesnt post images that i have uploaded. how do i fix it!