@Abcd123
I have been on here for several years.
My pattern has been to stay clean, then fall...but when I fall I usually fall again within a week.
Or a month.
I think three things cause this-
The Yetzer Hara teases you - it says "If you can fall once, then what is so bad about falling again?"
I read that the Yetzer Hara is not so concerned with making you sin once. It wants you to feel bad about yourself as a result of a sin, and so then sin again and again because you feel low and a big distance from Hashem.
I also think that the "high" of the fall makes our brain chase the high again, even more than before the first fall. We need a more intense high each time we fall.
So - know that you are not alone, and this experience is to be expected.
Keep going - take things day by day.
Be on extra guard after a fall, and be extra nice to yourself, give yourself lots of reasons to be positive.
And perhaps try Mindfulness?
Treat the urge to fall, as an external thought, rather than something that is part of you.