أحسن الله إليكم One of the pillars of la ilaha illa allah is certainty and not have any doubts, for the last few weeks I keep findind myself losing certainty and getting attacked by doubts so I seek knowledge to strengthen my iman and then repeat the shahadah but then the exact cycle happens again.

This is called OCD, and it is a psychological disease. The best solution for this is that you stop. You must never ever repeat anything (and if you want me to repeat the word "ever" a multiple times, I will). You should never repeat: 1. Your Salah 2. Your Wudu 3. Your Shahada 4. Anything at all If you find that you are not able to stop and you keep repeating these things, then you should go to psychiatrists and doctors who specialize in this field.