Hi Ruby,
I am sorry to hear about your CKD. First off - if this helps put your mind at ease a bit - most CKD's do not typically progress very quickly so whether you talk to your doctor today or tomorrow or a week from now, it should not make a significant difference. CKD generally progresses quite slowly, as in years, so depending on your diagnosis the chances are you have been dealing with this disease for years but it progressed unnoticed (it happens).
That said, there is no time like the present to safeguard your health so you should start modeling the behaviours that will protect what kidney function you have left. I'm sure you have read about them already -> limit salt and protein; stay away from all junk foods; get exercise; drink sufficient water during the day in order to avoid dehydration; avoid obvious bad habits like smoking; etc.
If your GFR is down to 26, I will strongly suggest you also limit your potassium as well. This means avoiding (or at best, limiting) high potassium foods like potatoes, tomatoes, oranges and bananas. This is because your kidneys cannot process and get rid of potassium as quickly as necessary, and highly excessive amounts of potassium in your bloodstream can lead to a heart attack. No kidding. Talk to your doctor about it.
Apart from that, you are right to be proactive about your health. In my experience, GP's are insanely busy and prone to shuffling through patients quickly (they are human, after all). I would simply make an appointment with your GP and show up. Period. Don't be shy about asking questions, but by the same token, don't be surprised if your GP displays a lack of knowledge about CKD. Their health knowledge tends to be more general in nature, and I was a little shocked to find that, over time, I became much more of a subject matter expert on CKD than my doctor! She didn't even understand how the kidney donor program fully works, I had to tell her. Bottom line is: ask your GP to refer you to a nephrologist (subject matter expert) as soon as you can get into one.
Lastly, a question: I don't understand how any doctor can look at a GFR of 26 and say "don't worry about it". GFR 26 means you have only 26% kidney function left; for perspective, most people start dialysis at around GFR 12 - 10 so you aren't that far off at this point (depending on how fast your CKD progresses - if it progresses at all). Surely there must be more to that conversation you had with your GP? What was the context? I just can't fathom any doctor waving away a GFR of 26 like that, it's inconceivable to me.
I hope that helps, and best wishes to you.