What does Pip worry about before he returns to Miss Havisham's in Great Expectations?
Your question is unfortunately very unclear. There are several key points when Pip in the novel returns to Satis House to see Miss Havisham, and your question does not pinpoint any one specific episode. I guess one key time when Pip returns to Satis House is in Chapter 27 when Joe visits Pip in London to tell him Miss Havisham desires to see him. Pip reacts instantaneously to the news that Estella has arrived back to Satis House and wishes to see him: the text says that his face "fired up" at the thought of seeing her again.
At the beginning of Chapter 29 we see what is preoccupying Pip. He casts himself in the role of the knight in shining armour, coming to save his princess, Estella, and re-building Satis House:
She reserved it for me to restore the desolate house, admit the sunshine into the dark rooms, set the clocks a-going and the cold hearths a-blazing, tear down the cobwebs, destroy the vermin - in short, do all the shining deeds of the young Knight of romance, and marry the Princess.
In Pip's fertile imagination, the situation is misread - he assumes Miss Havisham is his benefactress and that she has planned for him to marry Estella. This highlights one of the key themes of the novel - the way that characters are used and deceived by others for their own ends. Miss Havisham towards the end of the novel later admits that she deliberately played along with the idea that she was responsible for Pip's Great Expectations as a means of annoying her relatives. It is also this romantic view of his future which is ultimately shattered by Pip's revelation that Magwitch is responsible for his fortune and also Estella's marriage to Drummle.