dont worry as your 7 week negative test is a very good indication of your status..
drHHH in the expert forum says that he has never seen anyone who tests negative at 6-8 week,go on to test positive later..so the odds are on your side..
most people who got infected will test positive by 7 weeks..anyways you still have to repeat a test at 3 months as that is the guideline..most likely your result will not change..
never go unprotected in the future