Girls, could you please tell me what this might be? After conception, …

Girls, could you please tell me what this might be? After conception, we passed 15 days. On day 15, I had severe headache, nausea, my breast became more sensitive, and in the evening small bloody discharge appeared, slightly brown (for 6 days before menstruation). Bloody discharge lasted for 5 days, but it's definitely not menstruation because my period flows like from a bucket. I took a test, it turned out negative. My lower abdomen doesn't hurt at all, only a slight spasm. I read on various websites that implantation bleeding lasts for 2-3 days. I don't know what to think anymore, I'm very worried, and I have to go to the doctor only