Suggest Treatment For Sore Breast With Fluid Discharge

hey im 18 years old . My nipples really get sore when im walking outside and they stay sore till the next day . But i dont usually wear a bra maybe thats the reason , im not sure . I've been checking my nipples out and there red and sore and i've been squeezing them to see if any white discharge comes out but its not . Im also due on my period anytime now . Im worried thinking that i've got breast cancer because i smoke to. My dad said hes going to take me to see my doctor and have some tests done to see whats the problem , Can you give me any advice please . Thanks .