Since you had your periods there is little possibility of pregnancy
during first protected sex
Your feeling of bloatedness and constipation
is common in first time sex.
There are many proposed theories for this one is it may due to gasping lot of air throughout inercourse.
It may due to prolonged act which cause congestioof pelvic organs which causes pain.
Pregnancy dont cause any change in body in 2 days.
This will be corrected by experience.