How do I say I need to

I’m on Level 2 challenge 15. I can say most of the following sentence but an not clear about what I’m hearing on the ‘I need to’ part. The sentence is ‘I can’t remember how to say what I need to say’. There is an s sound that I can’t place. Any help appreciated.

I am going out on a limb here and guess that you are doing the southern course. For future reference, it is far easier to help you, if you provided that information yourself, and when it is about a specific sentence, it’s best if you provide the time-code where the sentence appears.
The Welsh sentence in question is Alla i ddim cofio shwd i ddweud beth sy’ eisiau i fi ddweud.

Thank you