That is the germinal disk. I do not see the classic "bull's-eye" that would indicate fertilization, but it may be too early for that to show up. Here's a link showing some great pics of fertile eggs:
these round marks werent showing up before now on the yolks though, and its now showing up on both of my hens eggs, and my rooster is just about 6 months old now, so thats the only reason I was thinking they are fertile. Unless you all can give me some good explanation of how all of a sudden both my hens have started laying eggs with this decent size round spot on the yolks now that my roo is old enough to make them fertile.
There will be a distinct, no mistake about it, bulls eye which that yolk doesn't have. I agree it looks sort of that way, but it's not. I've been looking at tons of egg yolks lately because my best hen, in spite of being covered by a roo, just isn't laying fertile eggs yet. AND I even tried to hatch some and no go.
Other than that, you'll just have to take our word for it. I'm sorry you aren't getting the answer you want.
PS - if you still aren't sure, let an egg sit out at room temperature for a day and then check it. If it's fertile, there might be a bit of a question when it's freshly laid but by the time a day or so has gone by there shouldn't be any doubt. That's sort of what it suggests in the wording at the top of the thread I linked above, and I've found it works for me. I wait a day before checking now at least. I know what you mean about the ring, I've questioned that myself.