Turtle roll and other bits of advice

After coming along great since starting surfing in June/July I have taken quite a few steps back in progress. I have gone from catching nice clean waves to nose diving ad missing waves this is because the waves have got bigger over the past couple of months.
I found that I could get out the back fairly easy by muscling my way through but now the waves have got that bit bigger I am not able to get out the back and when I do my arms are shattered. Which then leads to me trying for waves and missing them.
What I have found is anything over 3-4 ft I have to turtle roll and if I only have to do 1 then I can get out, 2 and I will get out eventually but my arms will be done and if I have to roll 3+ times I struggle to get back on the board quick enough to make progress before the next wave hits then I end up going backwards. I realise when it is over a certain size there is no point in getting out the back as I will struggle to catch waves as my arms will be shot, so I have taken the idea that when it gets too big I will play in the whitewater and practice my turtle roll and pop up, turning etc in the white water/ occasional green wave that comes through and when conditions are slightly smaller I can get out the back and work on pickin the right wave and everything else.
My questions are
Is there a better way of getting back on the board after a turtle roll? I just muscle my way back on but after 3 my arms are shot.
Is there anything else I can practice whilst playing in the white water? generally I pop up turn a little bit but it's not as good as catching a green wave.
Is there anything else I can do to improve my fitness? During the summer I got out quite a lot now I'm down to 1-2 times a week.
Anybody know of any spots around Cornwall that when it gets big will be slightly smaller? I have got used to going to Godrevy, gwithian and Perranporth.
Thank you for your time.
I found that I could get out the back fairly easy by muscling my way through but now the waves have got that bit bigger I am not able to get out the back and when I do my arms are shattered. Which then leads to me trying for waves and missing them.
What I have found is anything over 3-4 ft I have to turtle roll and if I only have to do 1 then I can get out, 2 and I will get out eventually but my arms will be done and if I have to roll 3+ times I struggle to get back on the board quick enough to make progress before the next wave hits then I end up going backwards. I realise when it is over a certain size there is no point in getting out the back as I will struggle to catch waves as my arms will be shot, so I have taken the idea that when it gets too big I will play in the whitewater and practice my turtle roll and pop up, turning etc in the white water/ occasional green wave that comes through and when conditions are slightly smaller I can get out the back and work on pickin the right wave and everything else.
My questions are
Is there a better way of getting back on the board after a turtle roll? I just muscle my way back on but after 3 my arms are shot.
Is there anything else I can practice whilst playing in the white water? generally I pop up turn a little bit but it's not as good as catching a green wave.
Is there anything else I can do to improve my fitness? During the summer I got out quite a lot now I'm down to 1-2 times a week.
Anybody know of any spots around Cornwall that when it gets big will be slightly smaller? I have got used to going to Godrevy, gwithian and Perranporth.
Thank you for your time.