I'd say that it is normal to feel like you are back at square one, in the circumstances you describe. But you won't be. Just go back to jog-walking, and you'll soon be back to jogging all the way.
As for getting to a 25 minute 5km in 4-5 months... that's quite ambitious for someone who feels that their weight/build make jogging a bit awkward.
But it's not impossible. Different things motivate different people, but I think you should set some intermediate targets down. You'll need to adjust (individualise) the actual numbers/dates here, but the milestones might look something like this:-
End of October - get confidence that you can jog non-stop for six km.
End Nov - get to 5km in (say) 32 minutes
Dec - 30 mins
Jan - 28m then re-evaluate your targets.
Don't just stick to running 5-6 km every time though. Have some runs that are just 3km... but a bit quicker... and throw in some slightly longer, slower runs when you feel ready.
I think I'd wait until the new year, to build up some basic running fitness - then take stock. Maybe in January you'll feel ready to introduce some more focussed 'speed' training that will really help you to reduce your times.
Enjoy the health and fitness that are just around the corner 