What Are The Side Effects Of Emergency Contraceptive Pills?

I am 23 year old healthy woman. I finished taking the contraception pill 2 years ago and since then my periods have been very light. I currently do not use any form of contraception apart from withdrawing and my partner is very careful. My current period however is extremely light. I have my usual other signs such as period pains and sore breasts but is worries me that my period is practically nothing and i have a weird twinging in my groin. This is all normal?