My periods are delayed by 16 days. it was supposed to come on 23rd July and has not come till now. my periods are always regular. but this time it's not coming. also I had done protected sex two times on 15th July. it was my safe period. I took pregnancy test two times on 28th July and 2nd August. it showed negative. I also had fever on 14th July. I took combiflam and some antibiotics. is my periods delayed​ because of medicine or m I pregnant or there may be some other reasons? because my periods are always regular