What should I do if I am doubting whether I am pure or not?

Recently, I have been having a lot of doubts about whether I am pure or not. The other day, I went to sleep for about an hour and after a few minutes of waking up, I went to the toilet and found a very small mark on my pants. I Did not know if this was urine or water or madhi. I don't remember having a wet dream or sperm release so I just washed it off. But now, I keep having doubts about whether I am pure or not. I am worried because I prayed and fasted in that state. Will my fast and prayers be accepted?