I'm on my period and i've noticed that these last few months i'm in more pain with a tampon in then i am a pad on, what could be causing this?

Tampon: My best guess is that your vaginal lining may be dry (not as much secretions as usual) and the tampon is causing more drying. Another cause could be irritation of the lining from vaginal intercourse or use of insertable toy, or reaction to latex condoms or spermicide. Try using a good lubricant- non-scented, water based would be best. If not better, see your doctor.