Missed period!

28 days po Ang cycle ko. Dec.9 last period ko, Jan.4 should start my 1st day, but nothing comes. Sumasakit Lang puson ko at breasts ko. Lagi din ako nilalamig. Nung Jan 6 ,I used 2 PTs, fainted lines pa sya. nitong nag 7days delayed ako I used 1 PT in the morning and it's positive. 1 PT ulit kinagabihan and I have 2 clear positive results. Yong una Kasi malabo Kaya inulit ko. Ask ko Lang po. when to start po , sa pag count if ilang weeks na tummy ko? thanks po.