No, those digitals are quite accurate, and generally a false positive is not common with pregnancy tests.
i'd say if you took 4 tests you're most likely pregnant.
I took a First Response digital test and got a positive. Here where I live in Reno, NV once you get a positive pregnancy test you have to wait until 8 weeks from the day of your last period. So I had to wait 8 whole weeks, to have an ultrasound to confirm my pregnancy, and my Dr didn't take any blood work. But it definitely sounds like a positive to me, good luck and Congrats!
I did 3 hpt all positive, one was digital too saying I'm pregnant. Do I need to have a blood test