I sometimes get doubts about my state of purity from when I go to the toilet. I try to analyze what happened and try and most of the time come to the conclusion that nothing Najis got on me, but I still get doubts. Am I considered ritually clean?
Bismihi ta'ala
We have covered the topic of waswasah and doubts in tahara a few times, and you are able to search in the Q&A on the topic of waswasah and taharah.
The simple rule of thumb is because you are doubting, you consider it all to be tahir. Nothing more.
Please watch this clip, which is a part of a lesson I gave on taharah and najasah. Hope it will be of benefit.