could a UTI or DIABETES disturb a urine test,i took 4 pregnancy tests only 1 was positive

Ok i hav a doctors appointment in 2 day, but im really really scared...i have had many signs of being pregnant, like nausea,back pains,i put on alot of extra wait, weird food cravings, I have to use the bathroom more often and i also heard your hair and nails seem to grow faster(MY HAIR REGUALRLY TAKE A LONG TIME TO GROW, AND MY HAIR ALWAYS FELL OUT,LIKE IN CLUMPS IN THE SHOWEROR SOMETHING, 6 MONTH AGO IT WAS TO MY EARS NOW IT IS A LITTLE PAST MY SHOULDERS,AND I HAVNT BEEN PULLING OUT CLUMPS OF HAIR LATELY)my peroid has been really irregular,i took 4 pregnancy tests and the first one results didnt show,the second was positive,and the last two were negative. I took the the second one first thing in the morning and the other 3 were later in the day....so because of the 3 failures i figure im not pregnant but i may have a uti or diabetes...(if i did have a uti or diabetes could it mess with the pregnancy test results)