I have yet to take any pregnancy tests, I think it is too early

This is my first post, bear with me! My periods range from 20-30 days, annoying. My last cycles (that I've kept track of) were 27, 28, 28, and 22 days. I remember having my last period over the 28th of June, but do not remember the start or end date, only that it ended before the 4th of July. What I calculated from my guesses of when my period occurred, my period should have arrived 2 days ago. Again, just a guess based on an approximate date of my last period, which could have occurred anywhere between the 25th of June an the 2nd of July. The week before my period I had protected sex (with a condom) and on July 10th I also had protected sex, again, using a condoms. Both times, condoms were checked before, during, and after sex. My usual pms symptoms are moodiness the day preceding the start of my period and cramps for a few hours or so during the night before it arrives. Lately, I've been feeling a tad nuseaus and dizzy when I stand, which can helped by eating. I am getting headaches recently as well. Also to consider: I have a hyperthyroid that I am taking meds to get under control, so that is probably being overworked. My uncle was in the hospital this weekend and suddenly, tragically passed away Sunday, so I am sad over that. I am freaking out over this, so much. I have stayed up late for the past 4 or 5 days doing all the research I can and all the searching I can. I am so scared and worried, I do not want to be pregnant!! I have yet to take any pregnancy tests, I think it is too early. When can I take one and get and accurate result? Please help!!! Thanks so much!!