Is it okay to take pregnancy test as early as before missed period?

I have experiencing morning sickness, back ache like stretching of my spine, fatigue, headache(parang ang gaan ng ulo mo pero masakit) urge to pee as in kahit hindi ka umiinom ng water you just notify na you want to pee, sore breast, sometime metalic taste sa water, and food cravings mostly in salty foods, 4 days before my periods starts, and last constipation and gas?