I've been seeing my work reposted without credits

This has been happening to me kind of frequently and increasingly over the last 6 months or so. I've been informed and shown by friends and others that they've found my work (particularly my League fanart) being re-uploaded and reposted on random imageboards, twitter, and tumblr. Without credit/a link back to me/a source. I know this is a problem for many artists that post to pixiv and tumblr (and I've noticed the problem escalating ever since I started using pixiv more). I just wanted to make my stance on this clear, in hopes that it will hep the situation even a little bit. Please do not re-upload or repost my artwork anywhere without crediting me, linking back to the original or my dA/pixiv, or otherwise providing the source from which you got it from. Luckily I'm already in the habit of watermarking like, everything :I I'm usually fine with people sharing my artwork as long as they credit me, but it's a different story if you're not crediting/linking back to me. Oh and if I find my work re-uploaded/reposted and the watermark has been removed/tampered with/cut off or otherwise made not clearly visible, there will be hell to pay. 

With that said, thank you to everyone to continues to watch and support me ;3; And thank you for reading.