Standing up, help??

This is the form:
I'm 50 years old. I first surfed 4 years ago on a trip to Bali. Started with a longboard in the white water, slowly progressed to catching the odd wave before it broke.
4 years on I guess I've surfed around 50 times in total, over several trips. I didn't surf at all last year but cycled a lot, and worked out in the gym. I'm 5 foot 9 170 pounds reasonably fit and strong.
I tired of paying to rent boards so bought one last year. It's 6'6" with a reasonable volume, not super-thin or anything. I didn't get a longer boards because they are a pig to transport.
Now my problem: I'm half way through a 2-month trip to Bali and Lombok. My duck diving has come on a treat and my paddling is OK, I'm catching plenty of waves. But.... I can't stand up! I've spent hours reading on the internet and watching youtube videos. I can perform a pop up (with some difficulty) on dry land but when I'm on the water I go to pieces! I either end up with my feet very close together and try to adjust, or on one leg with my rear right knee on the board. I'm aware I'm not thinking too much about what I'm doing, my mind is filled with doing it very fast, before I hurtle down that cliff of water
I'm pretty sure I should be on a longer board but I'm a determined sod, I won't give up on this one!
Any thoughts or ideas would be really appreciated!
Cheers
Rich
I'm 50 years old. I first surfed 4 years ago on a trip to Bali. Started with a longboard in the white water, slowly progressed to catching the odd wave before it broke.
4 years on I guess I've surfed around 50 times in total, over several trips. I didn't surf at all last year but cycled a lot, and worked out in the gym. I'm 5 foot 9 170 pounds reasonably fit and strong.
I tired of paying to rent boards so bought one last year. It's 6'6" with a reasonable volume, not super-thin or anything. I didn't get a longer boards because they are a pig to transport.
Now my problem: I'm half way through a 2-month trip to Bali and Lombok. My duck diving has come on a treat and my paddling is OK, I'm catching plenty of waves. But.... I can't stand up! I've spent hours reading on the internet and watching youtube videos. I can perform a pop up (with some difficulty) on dry land but when I'm on the water I go to pieces! I either end up with my feet very close together and try to adjust, or on one leg with my rear right knee on the board. I'm aware I'm not thinking too much about what I'm doing, my mind is filled with doing it very fast, before I hurtle down that cliff of water

I'm pretty sure I should be on a longer board but I'm a determined sod, I won't give up on this one!
Any thoughts or ideas would be really appreciated!
Cheers
Rich