Plan B affecting Period?

Hey i could really use some advice/assurance on this. I’ve taken plan b once before, and felt a little sick the first few days afterwards. i took it again on monday the 22nd (my last period had started on november 14th, ended on the 18th). and i thought i started spotting last night (the 26th) which i know is normal after taking plan b, but today it’s a lot heavier (enough for a tampon, and the color now is more like my period than spotting). has anyone else had this happen to them? should i be concerned that my period started so soon after taking plan b? any help or advice would be greatly appreciated!