Starting Birth Control For The First Time, Feels like I’m pregnant!?

I have been taking birth control for four days now and I am so sleepy. My breasts are sore and tender (which has never happened to me before even while menstruating), my head feels foggy and I’m tired. I keep getting cramps low in my abdomen and it feels like I have to poo but I don’t. Please tell me this is normal and I’m not pregnant. My partner and I were not using any form of BC (besides withdrawal) before because we truly didn’t think I could get pregnant. I’m not quite late yet, I’m supposed to start tomorrow but honestly my tracking might be off too. I’m a mess, help!