The last intercourse (protected, no accidents with the condom) was on November 5th. I got my period on the 11th of November as expected. I have not gotten my period since then. I have taken 6 tests, all negative. Went to the doctor and they did a vaginal ultrasound and found nothing. It has been almost a week I have had tender breasts and cramps (which is normal before my period arrives). Do you think there is any chance I could be pregnant ? I have also lost 5 kg this month only and I have had quite an emotionally and physically charged month. I do not if that plays any role with the menstruation cycle.

If the last intercourse was on November 5th, no intercourse since then, and you recently had a vaginal ultrasound, and also had a period after that last intercourse, then it's unlikely that you're pregnant. By this time, almost 7 weeks (if I'm doing my math right) after you last had intercourse, something would show on a vaginal ultrasound. Now that does depend on when you had the ultrasound. If it was a month ago then it may not show, if it was a week ago then something should have shown on vaginal ultrasound.

Stress, weight loss, weight gain, change in diet, change in exercise, and more can all effect your period.

I'd be willing to bet that you're not pregnant, you're just having an off month, but I can't say that for certain. There is a small, small possibility that the bleeding you had after intercourse was implantation bleeding and not a period. There is a small, small possibility that the pregnancy tests didn't register a pregnancy because you took them wrong, or it was too soon, or they were faulty. There is a small, small possibility, depending on when you had the ultrasound, that it was too early to detect anything. But based on what you wrote, I'd guess you're not pregnant.