Brown spotting after sex

Hi Girls! Just a quick question.. I had sex with my boyfriend yesterday and it was amazing but in one of the positions when he went inside me it felt a bit uncomfortable so we changed. I thought nothing else of it and carried on but this morning I had light cramps and I’ve got this dark brown discharge which has was looks like little bits of tissue in it? Has anyone else had this? I’m on the implant btw. Thanks☺️