Did those two test blocks wind up being the same size? Yes, they may have been smaller than expected, but were they consistently smaller? Did they match each other?
If so, I'd suggest that you just go with what you're doing now until you regain some of your confidence. At least finishing a quilt or two slightly smaller than the pattern called for is more rewarding than giving up in total frustration.
If all the blocks are the same size, it really doesn't matter if they're a tad too small. You can always make a wider border at the end, or even add another row of blocks, if you think the finished top should be larger. All is not lost, truly it isn't.