Hello and welcome to HCM.
Thank you for your query.
I have gone through your query, and am extremely happy you have mentioned everything in detail, but have missed out one very important point. Your sexual status. When did you last have sexual intercourse, was it protected or unprotected?
As you have had regular periods for quite sometime now, the appearance of an irregular one is indeed surprising. This could be due to the following reasons:
(which can be ruled out by a home pregnancy test [which as you mentioned might not be accurate, but only if not conducted properly]. You could go about a home pregnancy test by taking it at least 2 weeks from the date of conception or last sexual contact, or on or after the first day of a missed period. But please make sure you do so using an early morning urine sample this time, as it would yield a most accurate result)
-Infections: Are one of the most common causes of delayed periods, and also are accompanied by lower abdominal pains and cramps. Let me list few of the other most common symptoms of infections for your reference:
-Burning sensation while urinating
-Increased urge to urinate, but less amount of urine passed
-Lower abdominal and/or flank region pain
-Itching around the genitals
-Blood in urine or immediately after (not always seen)
Although not all symptoms need to be present. In such a situation as you are in, your symptoms could be related to pregnancy, which you will have to rule out either by a few home pregnancy tests
or by visiting a doctor. Or give your urine for analysis to a laboratory and write back to me with the results, which I will interpret and confirm/rule out the infection; or lastly expect a period (which can cause such symptoms). If the bleed was indeed an implantation
bleed, it should not last for more than 24-48 hours (this is the maximum, and is rarely seen for this long).
I hope I have succeeded in providing the information you were looking for. Please feel free to write back to me for any further clarifications at: http://doctor.healthcaremagic.com/doctors/dr-shoaib-khan/64581 . I would gladly help you.