Is this a withdrawal bleed?

Hi everyone, I’m a little concerned right now and could use advice... I have been on combination birth control pills for almost a year now. I’m good about taking my pills and I have only forgotten to take it once. I recently got into a relationship and me and my boyfriend have been having sex pretty regularly. However, we double up on protection and use condoms every time we have sex on top of me being on the pill. But I woke up this morning and started bleeding? This has never happened to me before while I’ve been on the pill and my period isn’t due for another week. Is this implantation bleeding? It’s light and on the dark brown side of things but it’s been happening all day. I’ve been nauseous all day and feel like I might throw up but not sure if it’s because of something I ate or my anxiety of possibly being pregnant. Should I worry?!