I don't think having sex isn't going to ruin your cycle's number of days, although it can help to start it if it is late and needs a little "kick" I think. You can take a pregnancy test as soon as you miss your period. Stress is usually the cause of amenorrhea unless you are pregnant, and since you have been really stressed out too, that's probably the cause of all this.

Remember February is a shorter month, so this could account for a slightly earlier period. Having sex the week before your period starts or during your period isn't going to get you pregnant, so you can probably rule that out too.

I think you are psyching yourself out But taking a test also helps settle things and eases your mind even if you only have the slightest worry and are almost sure you are not pregnant. Since you are pretty regular up to this point, then you can take a test with your first morning urine even up to five days before you think your period is going to start. Just remember that the accuracy of the test goes down the farther away you test......get the test that is specifically designed to give you answers five days before your period is expected. You are not required to use the first morning urine, but that is when you will have more accurate test results and I recommend that when testing earlier.

omg I have the same thing with my urine, i drank half a gallon of milk and it as like bright yellow, like a highlighter. not sure if thats related to prego though

I don't know if it's milk, but I had the same thing with that neon stuff my last pregnancy. I was pregnant many times before and never had that happen during the other pregnancies or when I wasn't pregnant. It is freaky isn't it? Nothing was wrong and the baby is fine.