My advice to you would be to stop using tampons and start using sanitary towels. Tampons are just too dangerous.
Go to Doctor to check before you are hurt
If you suspect there is any part of an old tampon stuck you need to get into see a doctor. Having a tampon MIA up there can cause severe infection and sometimes, if untreated, cause you trouble conceiving later on. You may need antibiotics if the doctor finds and extracts a tampon. Good luck to you!
Ellen