First, congratulations on the smoking cessation. This is a tough challenge and you've done it!
5Ks are a blast and what a great aspiration. Here's how you may well be able to break through that wall:
Mix it up with some interval training. That means your usual jog pace will have some push and release to it.
For example, you could start out your usual warm up pace. Maybe that is walk, or gentle jog.
Then, after 5 minutes, push hard for 30 seconds. Or find a landmark - tree or house, for example - in the distance, about 50 to 100 yards out. Run like crazy to it. Then, when you hit the mark, walk to recover. When you have your breath back, you can slowly jog another 5 minutes. Then repeat it again.
There are lots of ways you can mix this up, that's just one example. Of course, be sure that there are no contra-indications before you try interval training, with either circulation, blood pressure, or knees. That's my disclaimer.
What will happen is you'll push yourself in these intervals beyond previous conditioning. Then, in a couple of weeks, try the straight jog again. I'm betting minute 13 won't be what it used to be.
There are many uses for Interval Training
, and breaking a jog or aerobic conditioning plateau is one of them. Give it a whirl and see what happens, then get back to me and we can adjust according to what takes place for you.