I ran a 10k marathon last week
I'm not sure what you mean with the term 10k marathon?
A 5k is 3.1 miles, a 10k is 6.2, a half-marathon is 13.1 and a marathon is 26.2 miles.
So the term you used, 10k marathon, genuinely confuses me! If you just mean a 10k then I did an official chip timed 10k yesterday, it took me 55mins, and I've been running just 3 or 4 miles once or twice a week for 2 years to get fit enough for that time (combined with a weight loss diet).
My best half marathon is in 2hrs 10mins -again with the occasional running making me fit enough for that.
I'm not feeling ready for a marathon with the training I have done. It would take me at least 6 months of increased training I think.