false positive?

Hi ladies, so I've taken 2 tests so far and both have been positive. I'm about 4 weeks and 2 days so very early on in this journey. I have my doctors appt Thursday and will get my confirmation. My sister told me not to get my hopes up because she said her friend had a false positive. That her hormones threw it off and it said it was positive but it wasn't. Is this truly something that can happen? It totally burst my bubble.