in case of regular periods it is rare to have pregnancy
because of intercourse on 6th day.
if your periods are with 30days plus cycle length then these could be post ovulation symptoms,
anyhow as pre ejaculate fluid can contain few spermatozoa
if your periods get delay better to check for pregnancy once,
depending on the result you can proceed,
meanwhile you can take antacids to get relieved of symptom with your doctor's advice.