I had a blood test done 4 weeks and 4 days after sex came back negative. 9 weeks after I took 3 different.brands all came back negative. I also had 2 periods a bit late but had them to.I just don't understand because my breast are so tender and swollen with dark blue veins am I pregnant

No, it would be rare, are you having sex often ? You need to speak to your doctor why this is happening and have an exam.

No last time was almost 10 weeks ago

You're not pregnant.

Your breast will grow and change throughout your life even if you're not pregnant. Chances are you're just having a hormone spike or something like. I wouldn't be concerned about being pregnant, just make sure you have a properly fitting bra. Your boobs will thank you.