I have missed my period for the last three months, I have recently had unprotected sex but took the 48-hour ECP. What are the chances I'm pregnant?

89-95% protected. If you take it within 72 hours after you've had unprotected sex, the emergency contraceptive can reduce the risk of pregnancy by up to 89%. If you take it within 24 hours, it is about 95% effective. So somewhere between those two estimates. If you are not menstruating regularly then it is likely you are less fertile than if you were. The chance would seem low but best to do a test.
Well. Cant give you exact figures but this would be the number 1 thing I'd initially think to check. A urine pregnancy test will tell. There other various other causes for missed periods eg thyroid disorder, polycystic ovaries, effects of medications, stress etc so would be worth a GP appointment to look at these if pregnancy test is negative.
Missed periods . Missed periods can be due to various reasons but pregnancy is the commonest reason for it . Please get pregnancy test . .
Pregnancy. Get a urine pregnancy test done . Preg is possible.
Get a pregnancy test. While there are many reasons to miss your period for three months, being pregnant is at or near the top of the list. Get a pregnancy test before taking any more hormones.