Congrats !
I started playing on 6 Sep 2016 and reached L40 last November. From L39 to L40 seemed forever and those 5 million XP looked so unreachable. Since reaching L40, XP becomes meaningless and yet they seem to come so much quicker; I will soon reaching 25 million XP.
Do take care of your item bag before you hit L40. The added items will make your bag overflow and stop you from getting new ones, including those windy 10km eggs . Just my 2 cents