What Causes Pain In Tailbone?

My tailbone has been hurting for 3 weeks. Everytime I stand up it hurts really bad. Even worse when i walk. After a minute the pain goes away. Ive recently been getting headaches. I feel pressure behind my eyes. My stomache has also been cramping for no reason. I am a girl but its not my time. I have also been experiencing hip pain. This all started with my tailbone. Ive tried heating, icing and thereapy but its getting worse. Do you know what this might be ?