It is normal to pass some small
clots during your period, but the
clots you describe in your question were not normal for you. Abnormal clots can indicate a few different things such as fibroids, hormone fluctuation, miscarriage. It might be best to speak with your doctor and make sure that everything is OK.
The pain that you describe when removing your tampon, may be because it was a lighter day and the tampon was too large for the blood flow.