CD21 6DPO Implanation Bleeding? Maybe?

Since I've exhausted my "I might be pregnant" conversations w/my fiance I figured I'd get all of my obsession out here.

I'm an average 28 day cycle. My Last period was 8/26. I ovulated on 9/9 or so. I had sex 3x that week w/the "pull and pray" method since I'm not on BC.

Here is where I got a bit "uh-oh" ... on CD21 6DPO (This was 9/15), I spotted brown. It caught me completely off guard. I'm not due for my period until 9/23.

On 9/12 I started to notice tenderness in my breasts and on on 9/13 or 9/14 I noticed a creamy discharge on my panties and thought THAT was odd. Then the spotting. Of course I get online and start googling /calculating...

As of today 9/17 (CD 22 7 DPO) I have now had a very very light brown mucousy thin "spotting" only when I wipe. However the center of my pelvis (base) is achy ... sort of full feeling. I have NO Idea if I'm experiencing way too early PMS (Although after snapping at a group of friends via email I would have thought so) OR if this was Implantation Bleeding.

Some other "quirky" symptoms...the past week I've been overheating around mid afternoon. To the point I'm undressing to be cooler and putting the AC on at work.

I've also had bouts of nausea and I've been VERY gassy and I'm also starving quite a bit lately. The other night I went to bed starving and couldn't understand why. I ate dinner. I couldn't wait for breakfast when I got up the next day.

The calculations would prove I'm right on target if I did indeed conceive. Am I wasting my time thinking "this is it" and how soon should I plan on testing if I can prior to 9/23 AF tentative arrival.

If you followed this, great job -- I can never follow these questions with dates, etc. so if you can give me any sort of yeah/neah that would be great!

Oh and I should say...I have a 12 yo daughter so it's been quite a while since I went through this and with her, I was 21 with absolutely NO Symptoms (easiest thing actually!!!)