Do I have an STI?

Hey guys, this is my first time posting, but I went to the doctor think that I had a UTI ( I get them quite often and can normally tell when I have one). However, the test came back negative and the doctor asked me if there is a possibility that I have a STI. I said no because my mom was in the room ( I am 16), but I have had sexual contact within the last month and was wondering if that might be it. I was having discomfort and frequent urination and I wasn’t supposed to start my period until this week, but I was spotting all last week and have been having discharge. Do you think this could be a STI? Should I talk to my doctor? The only reason I am asking is because I do not want to have to tell my parents if I do not have to. Thank you all!