Just Vent | Just Venting

I'm not sure what to do yet? me and my boyfriend had unprotected sex on the 19th of august. I was expecting me period on the 25th but it hasn't came yet. I'm usually right on target with my periods. I'm having pain in my back and some cramps in my lower stomach but they are really light cramps and they only appear every now and then sometimes they can happen 2 to 3 times a day and then none the next day. I'm not exactly sure what is going on so someone please help me? I'm pretty sure it's too early to take a test. pls help asap!