So some problems happened when uploading my book to both Blurb and Issuu.com. With Blurb the size wasn’t right even though it was right in my InDesign document. It was repeatedly too small but changing the size even to be bigger for some reason never helped and it wasn’t until I made my document the exact size it said to make it in inches and removing the bleed setup that it worked. It also took a while to figure out how the site wanted the cover pdf to be uploaded (two landscape pages, one for outside cover and one for inside cover). But after that it finally worked!
Issuu.com presented another problem which was that the pdf Blurb made for me (combining my two pdf files containing the book + cover) took away some of my images. The yellow patterns for example that I had on my chapter pages transformed into solid yellow pixelated squares. Very very strange. And annoying because it cost 3 pounds extra to get that pdf. In the end I had to combine my pdf files myself through adobe reader and then the issuu version worked. Good to know! (not paying for the blurb pdf again hah).