Popping Pelvis

Iv had a popping/cracking pelvis since I was 15 and have no idea as to how it came about.
It started on my right side and I started going to physiotherapy and it was fine for a while but then it started getting worse after that I then went to see a chiropractor and it was fine for about a month.

I explained to them about having a sharp pain that started from my coccyx bone and shot up the right side of my back when ever I moved in certain ways and they had told me that I had put my pelvis out of place. This carried on for a few months and I eventually had to stop playing football as it got worse and worse it’s been fine for about a month now but this popping/cracking has now started in my left side whenever I raise my left knee towards my chest and it happens every time I do so this has been going on for 3 years now and is abit worrying as I’m only 18 although I had an x-Ray done about 2 months ago and they say my pelvis and spine were perfect I was just wondering does anyone on here have any advice or experiencing down thing the same or even know what this is.

Replys are appreciated thanks.