I have had sex with my boyfriend unprotected 4 days ago , I have been having bad heartburn , bumbling stomach & sleeping more then usual and weird mood swings , I have also gotten my period 2 weeks early , what can be the cause of this ?

Indigestion? If you are thinking about pregnancy, it would not be apparent with symptoms in four days.

It takes the sperm 2 to 3 days to even reach the egg. You would have no signs at all at four days. This does not mean you are not pregnant, it just means there is no way to tell at this point. In fact normally there is not normally any sign till you miss the next period.