So im on birth control called implonon and i dont get my period its been 2 yrs since i got it but a couple days ago i stareted spotting i thought it was my period but i usually have heavy periods and this one was very light and only lasted 3 days then i started to discharge brownish mucus like discharge my breast have been sore for 2 weeks now im having mild lower stomach pain and back pain i took a pregnacy test 3 weeks ago because i was feeling naseous at that time it came back negative so should i take another test or might these be side affects of my birth control???