blood test...sorry for preg post again

i really think i am pregnant i have all the symptoms and no period for 2 months and it never not comes ....i took had a blood test done last week but it came back neg however it wasnt at my doctor so i feel like hmm what if they messed up somehow its just strange how i have ALL the symptoms basically...so is it possible that it didnt show in the blood test yet??has this happened to anyone?? another reason im worried they messed up is cause i did the urine test first and the lady who did it called someone else over cause the second line was slight so i keep thinkin if i wasnt preg why would that even show??? sorry this is so long