What Causes Lower Abdominal Pain And White Discharge From Vagina?

Hi I'm having vagina problems I'm scared , so my problem is I'm on this birth control & I haven't had a period this month which is normal for my type of birth control but every morning we I use the restroom I have pains in my lower abdominal area to where it takes my breathe away & I have to push really hard tell the pain is gone but then there's a white lotiony discharge wit a little red in it . but rite now I still have the white discharge but its starting to get a bad smell but I keep it clean down there . Im also having lower back pain bcuz of it . I went to the doctor & got checked for std's everything came out negative but my ph was 6 I think which I think mean an infection I'm scared plz help me