Random bleeding?

I've been on Lo Loestrine Fe for a year and a half. I had a period about a week or two ago. I got on a plane Friday and after that I started having brown blood and cramping. My mom joked the air pressure on the plane could have caused it. I was taking my withdraw pills but I never bleed on them. I track the days I had sex, could it be implantation bleeding or am I overthinking it? I've been super tired, keep getting headaches and my back hurts but it could be from traveling.