What Causes Spotting And No Regular Menstrual Period?

Hi, may I answer My last period was normal and it started on Feb 20. I've never missed a period before and they have pretty much always been on time! I should be starting my period right now, and i might be or i might not since im spotting.
I ALWAYS know when my period is about to start. I'm never caught off guard about it. My inner thighs begin to hurt with this like deep muscle pain that can get so bad that it will affect my daily life if i don't take any pain relievers. The first day this pain starts and usually my lower back will hurt too and sometimes my lower abdomen too. These pains come like clockwork and I can always expect to see period blood sometime in the next couple of hours!

I knew my period was going to be coming some day soon since it's been just short of a month. My periods are on more of a 30 - 32 day cycle instead of 28. My period usually starts a couple days later than it does the month before. But right now it's only the 19, so it's kind of a couple days earlier than I would expect it to be, but that's not really worrying me. Anyways I went to the bathroom yesterday evening a found a brown spot on my panties and it was soooo unexpected! Like i said, i ALWAYS know when my period is starting because these pains ALWAYS start first, but i felt fine. Along with this brown (old blood) spotting, i felt a little nauseous from about 8pm till about 2am when i went to sleep. It was bad at all, and it was more in my head than in my stomach. It was just a slight feeling that didn't stop me from doing anything, it just kind of annoyed me. I'm not sick and I didn't really eat anything bad. So that's when i started getting confused. Nausea and unexpected period was unusual!

I figure that when i woke up this morning, i'd feel my normal leg pain and everything would be normal. But i was wrong. It's going on 7pm and I've felt normal all day! No leg pain like usual or any other pain. My slight nausea went alway also. I've been spotting all day, and now it's turning to bright red blood, i guess because all the old blood is gone. This is normal for me anyways. My first day of my period is usually brown then it will gradually turn to fresher blood. Anyways, i'm still spotting. Sometimes it just a tiny bit, other times it's a pretty good bit. Once again, no period pains at all !

There is a slight chance i could be pregnant, obviously or i wouldn't think twice about this. It's just really weird to be spotting and not be having a normal period flow on my second day, like usual and with no pains. I will continue to monitor this and maybe tomorrow things will return to normal.

I know that some women don't miss their periods when pregnant. Maybe this could be my missed period and i'm just spotting? Or maybe this could be implantation bleeding that's just happening at the time of my period since. I know that implantation bleeding occurs at least a week after conception and that sounds about right according to the times that I've had sex.

What does this sound like, since i'm spotting and have no pains? My breasts don't hurt either. I have no pregnancy symptoms at all, which is normal because even if i was most women don't experience any till a couple months into it.

Also, is it too early to take a pregnancy test. I know your suppose to take it in the morning and after your missed period. Do you think i should go ahead and take one tomorrow morning or should i wait a couple of days until i see if this spotting turns into anything else? Should i get a normal pregnancy test or an early detection one?

Thank you. :)