thanks for your query.
I assume you are talking about the threads of your intra uterine device.
As the question mentions " oil " threads which is definitely a typo.
Feeling for the thread is a method of confirming that it hasnt slipped out.
But there are other more reliable methods.
Please visit a gynecologist who would try to visualize the threads per speculum.
If not seen, then the device placement and position can be confirmed by a transvaginal pelvic ultrasound
where it would definitely show up.
Other options include having a hysteroscopy
, removing the device, and having a new one fitted with intact threads so that you are not so anxious.