Is pink discharge a sign of pregnany?

Ok let me just start off by saying my periods are very irregular and I didn't have 1 at all in December and my last 1 was early January, I had sex on the 21st Feb and 2 days later I had pink discharge when I went to the bathroom, a couple of hours later I was spotting and the next day as well, it stopped for abit but 2 days ago when I went to the bathroom the pink discharge was there again but was lighter in colour and I had a horrible cramp/pain in my lower right abdominal almost like pms all night :-( and yesterday and 2day its mild but in the middle of my abdominal my discharge now is sort of clear and stick what does this mean? does it sound like implantation bleeding can that happen all in 1 week? or an infection?