What Causes Left Sided Pain In Lower Abdomen With History Of Endometriosis?

I was diagnosed with endometriosis last July with a laporoscopy, I was told to go back on the pill due to this. I have been taking the pill as told to by the doctor. the past two weeks I have been getting left lower abdomen pain and the past 24hours have been very sever and painful, not sure if I should contact my gp and go for an appointment or if I should go straight down to the hospital