A positive and two negatives

Me and my boyfriend haven’t been the safest recently and before I took my second Plan B in 2 weeks I got a pregnancy test to make sure I wasn’t already pregnant and going to harm the baby by taking another Plan B, and the first one said error and the second one from the same box said pregnant. I then got two more tests from two different stores and those were both negative... I believe I have a bad uti and I saw that that could be the reason for the positive test? Anyone have this happen to them?