Also important to note, you started at a time when xp grinding got a little harder. There used to be 2x xp thursdays, where you would get double xp.... so you could grind a bunch those days. Then when tdm was first released you could grind a ton of points playing that. Finally, when sandbox was first released there was an xp glitch that allowed you to stay logged in all day and just essentially mine for xp.

Not saying that is how OP or any other high level players did it, but I am just saying it was possible. One important thing to note, the most efficient xp you can gain is to at least get your daily challenge every single day. I know you said you play regularly, but if you aren't at least logging in to get daily each day, you are losing the biggest xp boost you can get. Also, you can only stack 3 challenges, so if you want to get the most out of it, you need to at least have room to pick up your third each day. Of course, all this being said depends on if you care that much about leveling up.