Hi,
If you have been using the birth control continuously and not missing dosages in between, the chances of you getting pregnant even if you had unprotected sex are small.
Yes
nausea and heavy/full breasts are a sign of
pregnancy, but the fact that you're on the pill, home
pregnancy tests are negative all point to you not being pregnant.
Another question worth asking is did your boyfriend pull out on time the last time you two had sex?
So just wait till your period starts in three weeks, it will be the best sign of you not being pregnant.
If you are still worried, go to a doctor and ask him to run your bloodwork for signs of pregnancy.
But from what you've said so far, I find the chances of you being pregnant very small.
I hope this answered your question.