Belgium international Lukaku scored 16 goals in his first 13 games of the season for club and country but has not found the back of the net for United since September.
The 24-year-old ended a seven-game goal drought with a brace for Belgium against Mexico on Friday and says United’s dip in form made it ‘more difficult’ for him to get on the scoresheet.
‘Lately we haven’t performed like we did at the start of the season, we started by blowing teams away, being dominant and creating chances,’ summer signing Lukaku told Sky Sports.
‘But in the last few weeks we didn’t play at the same level and that made it more difficult for me.
‘That’s the sort of thing you have to go through in the season, but now there are players coming back from injury and hopefully we can deliver performances even better than at the start of the season.
‘We can create more chances and more goals.’
Manchester United 2017/18 Fixtures
Newcastle United (H) – Sat 18 Nov
Basel (A) – Wed 22 Nov (Champions League)
Brighton (H) – Sat 25 Nov
Watford (A) – Tue 28 Nov
Arsenal (A) – Sat Dec 2
CSKA Moscow (H) – Tues Dec 5 (Champions League)
Manchester City (H) – Sun Dec 10
West Bromwich Albion (A) – Sun Dec 17
Bristol City (A) – Wed Dec 20 (EFL Cup)
Leicester City (A) – Sat Dec 23
Burnley (H) – Tues Dec 26
Southampton (H) – Sat Dec 30
United started the season in sublime form but have lost two of their last three games to fall eight points adrift of Manchester rivals City.
Lukaku, who joined United from Everton last summer in a deal that could reach £90million, admitted it was a ‘relief’ to end his drought for Belgium.
But the striker never doubted his ability to bounce back, calling himself a ‘leopard in the box’ who was ‘born to score’.
‘It’s a relief but I knew it would come,’ Lukaku added. ‘I feel great to be honest. I was born to score.
‘I don’t think many strikers of my generation have as many goals as me. I am like a leopard in the box.’