Help please!

My boyfriend of 6 years and I just had sex and I started the birth control(the pill) this morning and he just finished in me! What do I do? I definitely think I should get plan B but I’m not ready to get pregnant. My periods are extremely random and I never know when I’m going to get it to to other health issues and I don’t know if I’m ovulating or what. Ugh I’m stressing, someone please give me some advice.