Lower left side pain in the stomac! help ? DOCTORS NURSES?

I'm 20 years old. I had a DNC in 2006. I had my period on Nov 2 and it ended on the 10 of this month. I have had intercorse but used the pull out method. I having belly pain. Also im having back pain, felling tired all the time, shakey. today when i got up i noticed when i wipe there was alittle bit of red blood. I did have intercorse on 5,6,7,8 of this month and the 22,23,24 of this month. What could it be. i dont have any STD's either.