Gear selector trouble

Hi
I hope this is in the right place!

Iv had my 2006 defender a year now and it’s just done 100000 miles.

basically last week when changing gear, it got harder and harder to change up into 3rd and down into 4th... then today I kept going into 4th instead of reverse and when changing down from 3rd I was going to into 4th instead of 2nd...
The best way to describe it is, it feels like all the gears have moved over to the left...

If anyone has any ideas what the problem is that would be great as I’m not the most mechanically minded and have no clue

thanks in advance!

J

When you are stationary and the engine is idling, and you depress the clutch and push the gear lever forward, it should go straight into third gear without having to move the lever to the right or left.
Does it do this?