What Causes Pain In My Pelvis?

My problem started in bath room. In one of the days last winter, it was in the morning and I went to bath room from bed being in hurry to take cold bath. There, when I was washing my body being in crouching position, I felt a pain and “ga” sound at my lower back as if there is misalignment. After that I repeatedly feel pain to my front pelvis, especially after taking bath. I feel pain for anything pressing my pelvis, especially belt and trousers. Kindly advise me for the cause and solution.