Pregnancy or something else?

I’m on the pill and take it fairly well but the other day I had some what I thought was break through bleeding. It was pink and light. I put a pad on but nothing was on it in the morning so it was just that tiny bit. Anyway since my boobs feel so sore and heavy and I keep having headaches and feeling sick. However I missed a period with my pill the other day, could this be why I feel like this or could I be pregnant