Thanks for Healthcaremagic,
You had sex just after your menstrual cycle which is safe period,because ovulation takes place in mid cycle approximately 14 days prior to next expected period.
If there are no more sexual exposure then chances of pregnancy
Your cramping and headache ,backache
and swing in mood may be due to some other cause like infection or hormonal
In case you are planning to conceive then you should have sex during this fertile week to increase the chances of pregnancy.
If you have any doubt please consult Gynecologist to examine you to see if there is any infection or other cause of pain.
Hope information helps You.
Dr.Akhilesh Dubey M.D