Trying not to think the worst

Last week I went to the doctor and had some regular blood/urine tests done. Just routine tests.
I was actually hoping the tests showed I had low iron, or something like that, to explain why I could be so tired lately. Something minor like that, that I could take a pill, and feel better.
Well the blood test results were okay, but the urine test showed blood. (that's called hematuria). The doctor explained alot of times this is a symptom of a bladder infection, but could also be a sign of something more serious, such as kidney/bladder problems. Cancer specifically. The doctor mentioned as well, I may have to go to a urologist. This was all mentioned so fast, my head was in a bit of a spin.
I actually have had some problems with going to the bathroom lately. But I have only had bladder infections a couple times before, and this does not seem like a bladder infection. I assumed maybe because I am 43, and have had 4 kids, that well.....it was an age/woman thing.
I was given another requisition to go to the lab for another urine test, as well as a requisition for an ultrasound(this was for if additional urine tests I was going to have, showed blood present again). I did another urine test before leaving the doctor office. 
That night, I got a call from the doctor telling me to forget the lab visit, and book the ultrasound right away, as I had "significant" amount of blood in the second test.
The next morning, I made the appointment for the first available date. Turns out I will get my ultrasound on my birthday, Nov 14. *sigh*
I'm sure I'm not the only one who tends to think the worst when certain things happen. The what ifs, and what would I do, always seem to come out, even if  you try to be optimistic.
My course is set to start in December, now I am questioning if this is something I should go ahead with. I have my interview with the lady who runs the course, a few days before my ultrasound.
I know we can't live life, wondering, what if, but..........what if....?
What if, I go ahead with this course, then find out I am not able to do this? That would be much worse scenerio, then if I put the course on hold and find out, I am healthy.
I do feel like my life is on hold somewhat, until I get a clear picture from the ultrasound.
I feel I am preparing myself for the worst. Is this what doctors do, when they tell us, you could have, this?
So I cannot just pretend this isn't bothering me, and I do know I could be un-necesarily worrying, but well, wouldn't anyone?