If you don't mind, I just want to make sure I'm not doing something wrong-- I'm breeding a local (US) Eevee that I caught and an Italian Eevee I got though wonder trade, I've bred and hatched at least 300 eggs and I still haven't hatched a shiny. :\
Even though the Masuda method does GREATLY increase the chance, it still takes a long time (usually)! In gen V, it was still over 1 in 1000 even with the Masuda method (but it was a lot better than the usual 1 in over 8000 that it was in gen V). It is more likely to get a shiny in gen VI, but I don't know exactly how much the Masuda method has increased the chances for gen VI.
There are people that still have to go through over 1000 eggs to get a shiny, it takes patience. 300 is nothing. Just keep going at it, and it will pay off. I've gotten a shiny within three eggs before, but I've also hatched over 1000 to get a shiny. It's all worth it in the end to get something you really want. uwu
Good news is that you can use this time to your advantage and work your way towards some great IVs and natures. I did that with my shiny Shroomish, and have a pretty good shiny Breloom now.