How To Diagnose Sexually Transmitted Disease?

Basically, i am worried that something is wrong with me? Maybe an STD or something. A couple of months ago, i was told i had gonorrhea, so i went to the doctors and they gave me a shit, it supposedly went away. I have had unprotected sex before, but i stopped having sex all together after i found out i had that std. I got on the depo shot maybe June 6, I ve had symptoms of course. And, on July the 13Th i started my period. Well, it finished but i was still spotting? I m sure that s normal. Yesterday however, i had sex for the first time in a long time (we used a condom, and i m still taking the depo), and of course it hurt a little, but after i noticed there was blood. Not a whole lot, but spotting, and it wasn t my period. My vagina after was sore, it hurt and was puffy? The blood continued then after a couple of hours it stopped. Then, maybe two hours ago i took another shower and noticed an uncomfortable feeling in my vagina, so i got in front of a mirror and looked at it, and with my finger i saw there was discharge, and it wasn t the normal clear or white color, it was a brown discharge but in a clear substance. And, i m really worried as to what it might be. I ve been looking on the internet for about an hour now, and it s too early to go to the doctors or anything, but is it another Std, or what are your thoughts on this? HELP please.