How long should I wait to test again? I need someones advice that has had this happen to them?? Please?

I was due to get my period yesterday and I still havent gotten it today! My partner and I have been trying to conceive. I got my period last month on the 16 and have about a 27 day cycle. I have never been late or missed a period. I have 2 daughters 2 and 4 and we are trying to keep the 3rd about 2 years apart. It hasnt been that long since I have had them but I dont remember. Has this happened to anyone else?? Ive gotten all negative pregnancy tests but no period. I havent stressed about it, all i have had is a bit of queasiness, headaches, and thing that normally dont smell bad to me are making me queasy. Im not making these symptoms up because other people have noticed them too. Is it possible to not get a positive result right away? how long should i wait to test again??