My 16 Year Old Brother Had Sex For The First

My 16 year old brother had sex for the first time but failed to use a condom. He has been complaining about a burning sensation when he urine and has been feeling weak. It's been ongoing for about 4 days. We've taken him to the ER and he was diagnosed with a UTI. He is now complaining about blood in his stool. Is this normal when dealing with a UTI. Or what could be the problem?