Can tampon (mostly) or douching (rarely) caused hydrosalphinx? I don't have any std, never miscarry, never had surgery, iui, or trauma in pelvic area.

No. Tampons and douching cannot cause hydrosalpinx. Hydrosalpinx is commonly caused by an old infection in the fallopian tubes. These infections may be caused by a sexually transmitted disease (pid). Other causes include previous surgery (particularly surgeries on the tube) or severe adhesions of your pelvis.
No. Tampons or douching don't cause a hydrosalpinx (a blocked, swollen fallopian tube). Hydrosalpinx most commonly results from past std's like chlamydia or pelvic inflammatory disease, which may not have been diagnosed or treated. Endometriosis or previous surgery, or a ruptured appendix with infection of the peritoneum, can also cause scarring around the tubes or blockage of one or both tubes.