The attacking midfielder attracted major approaches from Chelsea and Manchester United during last year's two transfer windows, but he ultimately chose to stay.
At the end of January, Fermin was rewarded with a new contract until 2031.
The 22-year-old told Cataluyna Radio: "It was a bit complicated, I felt a lot of pressure, but I never wavered. I couldn't say anything."
A few days ago, El Chiringuito reported that Manchester United are now ready to pay €100m for Fermin.
"Barça extended my contract and I am very grateful. As far as I know, I would like to stay here forever," he added.
"The truth is that I see myself there. There is still a bit left in the season, but I am really happy to be here (with the national team), and hopefully I can make it to the WC."