How can I go back to losing 1kg per week?

Ilona_loves_cats

I have been in a calorie deficit for 3 months now and since then I have lost 20kg. I allowed myself to have a cheat day when I reached 80kg and I did and it was also my birthday (same day) I ate maintenance that day, it has been 3-4 weeks after that cheat day and I'm now struggling to lose 1kg per week. I don't know if that cheat day affected my metabolism or what, but now the progress is unbelievably slower and it's messing with my mental health, please help.