Hi,
Welcome to the forum. I am really glad to help you out. Pregnancy definitely is the first thing which needs to be ruled out in view of the symptoms you are going through especially as you had unprotected sexual intercourse. I would suggest you to get your serum HCG levels estimated since this is more specific than urine for pregnancy test & it gets elevated in blood much early (around 10 days after the implantation of the zygote, formed by the union of an egg and a sperm).
The urine pregnancy test is usually done around 1 week after the missed periods. The HCG (it is a hormone) levels rise only in pregnancy and its presence will confirm the status of your pregnancy. It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care.