I understand your concern. I will help you to the best of my knowledge.
The symptoms that you said are very vague. They do occur in the presence of the hormone Progesterone
. However, it does not mean that you are pregnant, all the time.
I understand that you have taken a morning after pill 3 weeks ago, but I am sure you will remember your last menstrual period. Please calculate your approximate date of next expected periods based on this.
If you do not get your periods even after a week of the expected date, then the chances of you being pregnant increase. Then, you may do a home pregnancy
Hope this helps.