Could I be pregnant???

Could I be pregnant??? I know it's not lightly but here it goes. My last period Ended on the 5 Jan, we had sex on the 8th Jan. Ive been having insanely sore and swollen breast and terribly upset tummy for the past 10 days to be exact. I took a pregnancy test and it was negative so I decided to try an old home made test and those results showed positive... I took a blood tests at week Monday and that also came out negitive. My boobs have since gotten even bigger and more sensitive... my mom thinks it could be a false positive or a false negitive... what do you think? This has never ever happened to my boobs before!