The 21-year-old converted a late penalty to secure a 2-1 victory over Croatia in the first leg of their Euro 2015 playoff at Molineux.
Berahino told reporters: "I am just feeling good every game. I am growing. I feel confident but I am just trying to take each game as it comes, and trying to improve every game.
"It's still only like a draw really because they've got the away goal. We have got to go there and make sure we finish the job off, make sure we qualify.
"That is all we are looking forward to, making sure we qualify."
Berahino has scored five goals in his last three games for West Bromwich Albion.