First time...

My bf & I had some really crazy sex on Sunday night, we had sex 4-5 times, I felt fine & was enjoying it. Yesterday after noon I started spotting, this has never happened to me before. This morning I woke up & I was bleeding, I had to put a pad on & I still keep bleeding. This has never happened to me, it’s the first time. Has anyone else ever experienced this? Anything to be concerned about?