Are the symptoms of a bladder infection and and STD/STI different?

If so, what are they?

My older brother kind of scared me a little. 

Long story short:

I went to the dentist, got a root canal, was prescribed amoxicillin, took a few doses, went to the doctor to be checked for a bladder infection, bladder infection test came out negative, BUT the doctor said it is probably a false negative due to me taking the amoxicillin since it hides bacteria, left w/ a prescription for CIPRO, I've taken a few of those, talk to my brother about the med., he said the only way he knew he had an STI was him thinking that it was a bladder infection... 

Now I was thinking about it, and I've been a little bit scared. I don't think I should be because my bf and I have only ever been with each other so ... 

Just trying see what the difference of symptoms is for an std/STI and bladder infection. 

Thank you! 👏🏻🙃🙂