Group b streptococcus? No heath problems, urine sample may be contaminated? I'm 19 yrs old?

Little concern. Group b strep is a very common bacteria in the vaginal tract that can sometimes be seen in the urine. It only becomes an issue when you become pregnant in which case you will need to be monitored.
Common germ. This is a germ commonly found in the GI tract and within the genital tract of females in 20-30% at any given time. It is occasionally linked to UTI's in women, and can cause a devastating sepsis/ pneumonia in a newborn born with it. Unless this was a clean catch & you have UTI symptoms I would not consider it a problem.
Very common. Gbs is common and generally doesn't cause health problems in adults, but could cause serious infections in newborns which is why we test for it. If found, we simply treat the mother with antibiotics prior to or during delivery and most problems can be avoided.