Plan B symptoms or implantation?

For the first time in my life I had unprotected intercourse and took plan B on Thursday. I haven’t been on birth control for about 4 years and my partner, who I’ve been with for 8 years, and I practice safe sex by using condoms. On wed night we were intoxicated and slipped on using protection. I took plan b one step less than 24 hours after. I had zero side effects but I started spotting and cramping last night (4 days after) and my symptoms are still continuing. My period isn’t due until around 10/9 but the pain is similar to my normal menstruation.

Has anyone experienced these side effects from plan b? If so, did you experience them 4 days later? Google is conflicting and it’s making me nervous that I’m having implantation spotting.

My blood is brighter than normal