late period, negative tests?

Sophie
Hey everyone! So my partner and I are trying for a baby and had unprotected sex on 7.5.17 and I am 12 days late today. I have taken 4 different pregnancy tests in the space of 13 days and all were negative! My cycles are normally on time. My stomach is often very bloated and I have been having headaches/dizziness. Also a lot of schoolglue/egg whites discharge Any advice? Thanks x