If you were having normal periods of 28 days, if you had unprotected sex between 10th and 18th days of the cycle, and if you had nothing relevant mentally or physically to affect your cycles, the present symptoms are pointing towards pregnancy
Why you did not get a positive result may be because of the time of testing. It will be positive from 7th - 10th days after a possible conception. That means from 25th day onwards your test must be positive if you are pregnant. If you have done blood pregnancy test it has a reliability of 95% and if urine was tested it is slightly less reliable than blood test
. Therefore there is a 5% or more possibility of tests going wrong.
If yours is a first pregnancy only you will have areolas becoming notably darker.
If you are mentally disturbed by a remote possibility of getting pregnant in the sense you do not welcome pregnancy, all these symptoms can appear even without a pregnancy. In that case, the cramps occurring now will be a precursor of your period. Gas in abdomen also can cause the disturbances similar to the menstrual cramps
. If you had taken contraceptive
pills either just before or even one or two months before, all your rhythm will be lost and will show similar symptoms without being pregnant.
Your short query without the details is not leading me to answer very correctly.
Therefore you are advised to visit the doctor as per your appointment and by that time, the signs and symptoms will become more evident for the physician to confirm or to rule out pregnancy.
With Best Wishes,
Dr C. J. Varghese