pregnancy tests

i need some advise on what to do as my period app says i'm 12 days late for my period and i keep taking pregnancy tests and i keep getting positive and negative results like i took a pregnancy test yesterday and it was positive but then i took a digital the smorning with first mornings wee and it said not pregnant i'm so confused its messing with my head i just wanna know if i'm pregnant or not :( i've tried ringing my doctors to ask for a blood tests but apprently they dont do blood tests to confirm pregnancy surley i cant get nearly 20 odd false positives