Was it a period or implantation bleeding? Still don't know if pregnant or not.

Hubby and I have not been actively TTC, however we have not exactly been careful either. We are not using any birth control and just started entertaining the idea of TTC soon, so we stopped using condoms and switched to pull out method. A couple of when I thought I was not ovulation he did not pull out and came inside me. Usually I have a 21 days cycle. Had lastp period on Sept. 1, so therefore I was do around 21 or 22. However before I was due, something felt "different" so I took a test. It was negative but after counting backwards I realized I took the test way too soon. On 25th (4 days late) I took another test and it was still negative. By then I was starting to have more symptoms. Breasts which are usually only larger on period have been large for nearly two weeks now, nausea and heartburn, constipation (I am NEVER constipated - go regularly 3 times a day), some headaches, some aversion so just looking at food, tired in afternoons, etc. The morning of 26th, I woke up and went to bathroom and when I wiped after urinating, there was a slight brownish color on on the paper and I thought my period had finally showed up, now 5 days late. My period is always the same. First day light "spotting" coming out that gradually builds during the day. Day 2, very heavy with bad cramps, day 3, still heavy but lessening, day 4, like the spotting stage and gone by day 5. This time however, day one was lighter than my usual spotting with almost nothing there, no cramps. Day 2 same as day one, almost nothing there, with light cramps. Morning of day 3 some bleeding, like a light period, more reddish in color, medium cramps, but both blood and cramps lessening. My question is, could this be implantation bleeding? I read that you should not test until after implanataion, because once implanataion occurs, that is when the HcG hormone is starting to be released and thus detected. Therefore, since I had such a light period and many symptoms of pregnancy, if there a chance I could actually be pregnant. And at what point should I retest to detect any pregnancy hormone. I was thinking of waiting a week past the bleeding to be absolutely sure. Thanks!

Kir