Milk like fluid after period

Today is Monday. My period lasts seven days and ended on Sunday. Sunday night I had sex and during it my boyfriend squeezed my breast gently and a lot of white fluid came out of my nipple. The liquid comes out when I squeeze either breasts and at one point it literally shot out. Its still happening today when I squeeze it. We did have sex prior to my period. I feel nauseous and exhausted and I have a headache. I took a test last night and it came out negative. People are telling me that maybe it’s too soon to detect and that I should wait. Im getting scared because google is literally saying I must have a tumor or a hormone imbalance. I am on prenatal vitamins but I’m positive they wouldn’t affect this. I’m going to make a doctors appointment tomorrow. I’m just wondering if anyone has any experience with this or knows something.