Abbey, I had a singular episode of haematuria a few years ago when working in Paediatrics. I mentioned it to one of the Paediatricians who was one of those very old school influential people and it transpired that his son was a Urology Registrar - I suddenly had an appointment the next day (Saturday) in the Urology Clinic. They did a flexible cystoscopy and found nothing, unsurprisingly, not even a hint of a UTI. I remember the Urologist I saw telling me that blood in the urine is not uncommon once in your life as it is a very vascular area.
I get the impression you are a young lady in her early twenties (correct me if I'm wrong) and I would be truly astounded if a woman of your young age was found to have a primary bladder malignancy. Sadly woman of your age do get cancer - but that tends to be cervical, breast or endometrial (hormone-driven cancers) or haematological. I don't think I've ever seen a bladder malignancy a woman as young as I am assuming you are. That's not to say it's impossible or has never happened.
However, it is very important that you call your GP and arrange to drop of a urine sample as if you have a UTI it could get nasty and affect the kidneys if untreated.
All the best and keep us posted.