Hello, I am 22 years old and have been in a sexually active relationship with 1 person for 1 year. I use the pill for bc. I have always been regular when it comes to periods - down to the time and everything! I am due on my period this weekend (Sunday) and since last week I have had an unusual discharge. It started off yellowy and is now brown in colour. It does not look or smell like blood. I am worried because for the last 6-8 months I have had a very dull ache in my lower abdomen (feels like dull period pains), it comes and goes but it's there more than it's not. I have had STI tests and come back clear. Has anyone else experienced anything similar? Please help!

Thanks in advance.