I'll get straight to the point. I've been having these lower back pains for quite a while and I don't remember exactly since when. However I can say that I usually get them when I'm bending or sometimes after/during floor exercises (usually when doing flips and twists). This pain is very stingy and if I don't keep my body straight it keep hurting until a few minutes have passed.
I've read somewhere that this might be a disc problem. I went to the doctors and got x-rays but he said there was nothing wrong. They were just "contractions".