The Poland international scored twice as Milan came from behind to beat Atalanta 3-1 in Serie A on Saturday. Piatek has four goals from three league starts since joining Milan from Genoa in January for a reported 35 million euros ($40 million). He also scored two in the Italian Cup for the Rossoneri.
"I always believe in myself and I know that I can always score," Piatek said. "But I admit that six goals in five games is a great number, more than I expected."
Piatek has netted 17 times in Serie A, leaving him just two behind Juventus forward Cristiano Ronaldo on the goalscoring chart.
Milan remained in fourth place and the final Champions League qualifying berth, four points ahead of Atalanta as well as Roma and Lazio, which both have a game in hand.
The Rossoneri are also just one point behind crisis-hit city rival Inter Milan, which hosts Sampdoria on Sunday.
"This team is like a family," Piatek said. "When I arrived everyone was nice to me and I feel good here. I'm scoring and that's important. We work a lot during the week, and we're getting to know each other and our movement's better."
Piatek netted his first goal of the night on the stroke of halftime with an absolutely stunning side-footed volley to level. He didn't even need to look at the goalmouth as he got in front of a defender onto Ricardo Rodriguez's cross.
Atalanta took the lead 12 minutes earlier when Remo Freuler's shot squirmed under Gianluigi Donnarumma's hand and in off the inside of the far post.
Hakan Calhanoglu fired Milan in front 10 minutes after the break with his first goal of the season, and Piatek headed in a corner in the 61st.
FIRST VICTORY
Leonardo Pavoletti scored twice to help relegation-threatened Cagliari to its first victory of 2019.
Cagliari came from behind to beat Parma 2-1 and move six points clear of the relegation zone.
Juraj Kucka headed Parma in front five minutes from halftime but Pavoletti bundled in the equalizer in the 66th and headed in what proved to be the winner five minutes from halftime.
Cagliari midfielder Cagliari Joao Pedro was sent off late following two yellow cards in quick succession — the first for a foul on Kucka and the second for dissent immediately after the booking.