How Long Does The Plan B (Ella) Pill Stays In

How long does the plan b (Ella) pill stays in your System.? I took it on the 8th after having unprotected sex then I had it again on the 11th but before I had too the plan b I was experiencing stomach pain and just felt uncomfortable after taking the pill everything had went back to Normal I had unprotected sex again on the 15th and after that I started sleeping a lot craving mood swings my period is 5days late now but I’m experiencing my period symptoms but no blood should I be worried about what happed on the 15th.? My last period was July 29th-August 2nd