Is this Implantation Bleeding?

My periods are ALWAYS like clockwork. I'm a heavy 5/6 day heavy bleeder on the 18th of every month. My last normal period was Feb. This March. I had a short, two day period on the 14th. It wasn't as heavy as a normal period, but I had tiny clots and it was more of a darker red. I thought nothing of it at the time. This March I had unrpotected sex on the 29th and in April on the 2nd. We normally use the pull out method but those two times he came in me. On the 5th and 8th I had maybe a drop or two of blood in my discharge, which had increased allot, which isn't normal for me. I started a light period on the 9th, which was mostly made up of light pink and brown blood. It wasn't a heavy flow, very spotty throughout the day, but enough to see it on a liner, It came and went and just ended on the 10th. Today on the 11th, I'm wiping mostly brown (TMI) and occasionally have a little bit of light pink blood. It's only when I wipe.

About a week before I started this "off" period I felt pregnant. I have never had any PMS symptoms but for about a week my breasts were swollen and VERY tender to touch, veins were popping out, I had a cross between constipation/direhha. I had headaches, lower stomach pressure and I had dizzy spells and hot spells. All of these have gone away since the start of this odd period except the veins in my breasts and headaches.

Does this sound like it could be implantation bleeding or something else? How long would you wait to test?