Thank you for your query at DoctorSpring.com
I understand your concern.
With your tubes clamped, there is only a 1 % chance of pregnancy. And where it occurs it is mostly because the procedure was not done properly.
Since it's been 3 weeks since you saw your boyfriend, hypothetically even if you were pregnant it would have showed up on the test.
So you should not worry about pregnancy.
Sometimes the hormonal levels fluctuate and these symptoms show up. It will get better once you get your period.
Feel free to discuss further,