I'm not sure, am I pregnant?

I have never been pregnant before. After just recently having for the first time I started experiences abnormalities with my period. It's not as heavy and doesn't last as long. I have stomach cramps like my period is starting off and on but it's not even around the time it should be starting. My are leaking white yellowish stuff, and my lower stomach is hard. Like if I tense it just a little theres like this rounded shell that's hard and travels up my stomach. Any advice? I have an appointment to go in and get it checked, but it's driving me crazy. Weird question but it couldn't be some sort of std right?