Pregnant or just the pill

Right I started back on a pill desogestrel I use to be on rigevidon but didn’t agree I didn’t start this pill on my 1st day of period when it said, prior to this I had had unprotected sexual but it was 3 days before my period got my period as normal but this cycle was longer than normal but I put it down to stress delaying my period. Now I’ve been taking the desogestrel for 2 n half weeks and I’ve started bleeding again wouldn’t call it a “normal period” as usually it is heavier but still got quite bad cramps, I know that this pill can cause spotting but it’s more than spotting now I’m convinced it could be implantation bleeding as I had that with my last pregnancy you’d think id know wouldn’t you. Just after any advice from people who have taken this type of pill if they have had problems with irregular bleeding. Thanks in advance.