Hi, After Having My First Baby 8 Weeks Ago, I

Hi, after having my first baby 8 weeks ago, I have my first period. I had the implant put in around three weeks ago. My period is very strange. I understand it will be different because of the two factors above but I am very worried. I only get cramps in the evening but they come with a sharp pain in my stomach. Also today I have passed a white, rubbery texture thing with my blood. There have been a few of them ranging in shapes and sizes. I've searched the Internet looking for an answer as it's the weekend I can't call my dr. What are these white things? Do I need to go to he hospital?