What is the ruling on doubting the completion of making up for past Ramadan days, and is it obligatory to make up for the days I missed due to feeling pressure in the uterus accompanied by slight arousal and clear, viscous discharge? Is it permissible to make them up now, despite doubting whether they were made up previously?

The greatest remedy for obsessive thoughts is to ignore them. You are not required to make up the days during which you felt the aforementioned fluid emerge, whether it was semen (maniy) or pre-seminal fluid (madhiy). As for the fluid you saw on the eleventh day, if it was yellowish, it is considered menstrual blood if it occurred during your usual period. You are only required to make up what you are certain you broke your fast due for menstruation, and the default is that you are absolved of what you are unsure about. There is no requirement for sequencing the days that must be made up, and when you have made up what is necessary, do not pay attention to doubt and obsessive thoughts.