Serious answers please. Thanks?

I have been having pain in my lower abdomen on the left side. It is right beside my and feels all lumpy. It was really painfull that i couldnt even walk for about an hour or so. Thought it was my period pains but normally my period pain lasts until the last day but the pain went away for a while but kept coming back until the next morning. Could starting the contraceptive pill have caused the pain? Or has anyone experienced this before? Im definitely not pregnant as im having my period.