If clear blue digital weeks estimator said 1-2

Actually how many weeks am I and why did the regular digital say not pregnant but other brand said pregnant and weeks estimator the same said pregnant is it even possible because my last period was last month and I was supposed to start on 8-5 but never came had sex 8-6/8-11 can it be I ovulated without having a period? Also I took a antibiotic only started it yesterday without knowing I was going to get a positive result on a few pregnancy tests could it cause a false positive Im really hoping that isn't the case