A period that lasts 4 hours??!!?

Yesterday, I thought I started my period. I had very light pink spotting on my toilet paper when I wiped. I grabbed my menstrual cup and took it with me. When I went to the restroom around 11, I was bleeding. The blood was dark like it usually is the first day of my period. I inserted my cup and went about my day. When I went to empty it before bed last night, all that was in it was some clumps of old blood. I left the cup out and haven't bled since. Could this be implantation bleeding? I am 11DPO. I really dont want to get my hopes up.