Suggest Remedy For Period Problem

Sir i m 19 years old and hv unprotected sex with my b.f on 23rd may .but his liquid didn't releas ,but it it happens from me...now my monthly period stopped till now 5th june...and heavy stomach pain happening every day frm 2nd june.
my monthly period is 30th of every month...till before it was regular but tis month it happening.
I also make hcg test but it resulted negetive.
plz help me sir ,advice me some medicines for continuing my period.