Missing pills after sex

Patient: A couple weeks ago I had protected sex and I am on the pill, which I am good at taking on time. I kept taking my pill like I’m supposed to after having sex but then I lost my pack and went without taking the last 3 or 4 hormonal pills before my sugar pills..I wasn’t sure if missing pills after sex would effect anything..I bled during my sugar pills like I was supposed to but now I am having some lower abdominal cramping, and I just switched birth control brands..I also wasn’t sure if that would have anything to do with the cramping.