The last time we had unprotected sex with September 14 and I had my last period October 13 and I had been having some bad cramps. I took home pregnancy test they came out negative. Got a blood test and came out 1-2 weeks pregnant. I am supposed 4 weeks pregnant and 2 days. How does that make sense if I didn't have sex in October?

With NO sex since your last period you aren't pregnant. With protected sex you could be pregnant. You only mentioned unprotected sec.

Number of week pregnant is figured often by last monthly period, so they are going by the information you provided.

Was the last period lighter ? Most likely they just estimated wrong date