Female Issues; Help.?

So ive been on birth control for like three months now, the shot. and that was my first shot since you have to get it every 3 months.. well its almost time for my next one and this is my first period ive had since i got the shot.. im 14, and ive had major cramps, like where i cant sleep and i can barely move.. well i decided to go to the bathroom, and it wasnt coming out so i pushed a little harder and out plops something out of my . being scared i didnt care about being sanitary, so i stuck my hand in and grabbed it, its like, gooey, and rubbery, and bloody, and when i opened it with q-tips it was in like a circle kinda. and its hard but squishy.. and theres blood inside it to.. please help.. im scared.