when should I test again

I'm 21 I have a almost 4 month old I had my first period on June 10th after I had her and my period have always been on the dot I've been having stomach/ side cramps I'll get nauseous occasionally and sometimes I feel kinda lightheaded my period didn't come on the 10th this month so I took some pregnancy tests but like it would show and then disappear and kinda look like it was super faint when should I test again the end of this month or next week since it'll be a week past when my period was suppose to come?