l discharge? More before period normal?

Ok, so I seem to always have l discharge. I know some is normal because it lubricates the and what not but how much is too much? Like a week or so before my period I seem to get a lot of discharge. I am a little scared because I don't know if this is normal or if maybe I could have something. I have been experiencing very very bad back pain lately and know that some stds can cause back pain. I think it is not likely though because the discharge itself is odorless but it can make my panties smell weird. I don't know, but I need some FEMALE help please. Or male if your a doctor. But I don't need any random guys that know nothing about what they're talking about just being rude. Anything helps! I need to make an appointment with my dr, she's just hard to get into. Thanks.