Today I started feeling nausea straight after my 5 K run, and vomited (not much, so most of meal must have been already absorbed) about an hour after finishing the run. I have never had nausea after running before.
I haven't got a lot of experience in running 5K, but I have improved my time from 52 minutes to 37:17 (PB today). Last PB was over 39 minutes, and I ran one minute and 46 seconds faster today.
Ideally, I would like to get just under 35 minutes. I am 10 kg overweight. There never was a plan about how to run 5K faster, I just go for runs and see how it goes.
Weather today was 24 degrees C, humidity 80 %, if that means something.