The pain you are experiencing may be ligament pain or spasm (a stretching, burning kind of pain in the left and/or right lower quadrant). This is normal in early pregnancy and as the uterus is better supported by the pelvic brim -- after about 20 weeks or so -- this should subside.

Back pain is probably the result of softening of the supporting ligaments and disks due to the elevation of progesterone. However, it could be related to bladder or kidney infection, so be sure you do not have an underlying urinary infection.

For the back pain, may I recommend Elizabeth Noble's book: "Essential Exercises for the Childbearing Year,". I would not give up exercise, but try those recommended in Noble's book, which are back sparing. Walking is still fine, but running can be hard on the back. Pelvic rock, bridging (on the floor with knees bent and lifting the buttocks into air), mini-crunches with bent knees and lifting the head on exhalation are good. Posture and good body mechanics are important to remember. Avoid bending over and curving your back, especially when lifting. Keep the curve in your lower back and your shoulders back. "Williams' exercises" are good, and most clinics have copies of these.

I would not worry about the discharge, as long as it does not cause discomfort or irritation or have an odor. It is most likely normal to the pregnancy.

I hope these problems soon resolve and you have a satisfying pregnancy. Good luck.