Birth control questions

Hello! I’m 27 y/o and it’s the first time in my life that I’m starting birth control. I’m taking the pills the ones that have 21 orange and 7 light green. My OB told me to start them when I started my period or when I was spotting for my period and that’s what I did. I started spotting on Friday and I had nothing Saturday and Sunday then I had some on Monday and today Tuesday I have a lot of blood, is this normal? I don’t know how birth control and periods work. Only know is the 21 orange pills have hormones and the 7 green ones don’t and those are for your period to come. Any help please