Yes, Yes Yes they can be caused by sex. I know i kept having that problem and i went to a urogligist and he said what happens if some woman are not deep enough for their mates penis, then what happens when he climaxes it can go into the opening of us and cause us to have UTI's.
He sujested in order to prevent this from happening is to be on a redgement(spelled wrong) with some antibotic like maybe Macradantin taking a 100 mg a per day would help that to not happen.
So i went on this and now i am fine.

Are You sure you are having UTI's? I went through a period where I thought I was having them but it turned out that I had a skin condition and Vulvar vestibulitis and it only felt like a frequent UTI. Dr's sometimes treat things as such before the urine is fully cultured.

Also, some uti's and yeast infections are caused by microbiological agents from one's anus getting either near the urethra or vagina so maybe you guy needs to pay more attention to keeping everything clean and separate.

Also it is good to pee right after sex to clear out any possible problem. If these suggestions aren't helpful, maybe find a vulvar pain specialist to root out your problem.

THANK YOU! you know?...I think you're both right at this point! Graphic Warning: He can go down on me and spit doesn't bother me but his ejaculate even stings sometimes. I have been given antibiotics before and it turned out not to be a UTI so thank you both because now I have a place to start...I will make an appointment with my gyno and be very specific this time...thank you again!

i had this sort of problem and it turned out i was having an allergic reaction to the soap he was using....the skin rubs making it thinner and more sensitive...we changed to a non soap alternative and used a little bit of lube for a while and it cleared up.