Home preg.test says yes blood test says no, my tubes are tied what does that mean? More questions in details.?

I asked a question similar the other day but now I went to the doc. so heres the situation now. I'm 25 yrs. old, had a bilateral tubal ligation done 5 years ago, (the one with the rubberband around your tubes). I missed my period, I took a home preg. test, it came back postive, took another came back neg., took the dig. test it said PREGNANT no ifs ands or buts about that one, anyways, I get scared (bc of the possibility of it being in my tubes) go to the doc. on Friday, he makes me wait until today to have bloodwork done. Over the weekend, I have brown show all day Saturday not much just some, so that confuses me, then last nite I start bleeding like my period (which it may be that) it has continued today, just not as heavy as my normal period would be. Normally I'm flooding during my first 3 days, this is seeming like my 4th or 5th day flow. So anyways, my blood work comes back today negative, so what is going on with me, I didn't get to see the doc. today, just the nurse they just act like, well you're not pregnant, but why would I be late, why would more than one test come back positive, what would cause a false positive? I mean even the digital one there is no mistaking that one, what could be going on?