First PP period

Okay Mama's, dish for me! I just started my first period since having my son back in August. I didn't even know it was coming. Before pregnancy/baby I had cramping and stuff before a period, but none today. I have a headache since this morning, but just thought it was no big deal. Went to the restroom since being home and low and behold my undies were ruined. SO all of that to say, how bad is this first one going to be? I've heard they are awful, so I'm freaking out 😭