Just had transvaginal ultrasound yesterday. lining was thin and skyla was in place. yet today i have excessive bleeding with blood clots, pelvic pain, dizziness, nausea... what could have caused this?

Did you have the vaginal ultrasound for locating the IUD position after its deployment yesterday? If, yes, bleeding is due to the IUD placement and you should contact with your doctor if heavy bleeding persists.

Thin vaginal lining and excessive manipulation of the probe can cause this- but that would have happened right away. Suggest you get checked by your Gyn right away. and let the ultrasound people know too.