Could Severe Abdominal And Lower Back Pain Be Due To Pregnancy?

Hi,
for 2 weeks I had a little pain when I peed, I thought it might be a bladder infection.. sunday night my pain got severe, and I had strooong lower backpain or abdominal pain,..
I got antibiotics and painkillers from my doctor Sunday night,.. but it wouldn't stop hurting so I went to the hospital yesterday where they checked my blood and urine, did a cat scan of my kidneys and did everything,.... no sign of kidney or bladder infection, my blood results are okay....
today.. my lower back pain got better a little bit.. but now my nipples hurt or are sore... I now have the fear I might be pregnant. I am using hormones with Evra, the birth control patch/bandaid...
Please help!