The 19-year-old is in the last couple of weeks of his loan deal and has impressed at Kingsmeadow.
After he was sent-off on his debut, McCallum bounced back to score four goals in the space of three games for the struggling Dons in January.
The youngster is thrilled with how his loan has worked out and wants to boost Neal Ardley's side's survival hopes before he returns to the Hammers on February 23.
He told the club's official website: "It (January) was a great month for me as I was starting games and scoring goals to help Wimbledon do really well.
"I got the winner against Rochdale and then two goals against Wycombe Wanderers. I maybe should have scored more goals in that game to help us to victory, but that's the way it goes as a striker.
"I expected to maybe score a couple of goals during my spell at Wimbledon, but not four goals in three games.
"Hopefully, I will get a chance to start again and get a couple more to help the club move away from the relegation zone."