Can I Still Get Pregnant If I Started Althea Pills On The 3rd Day Of My Period And Had Unprotected Sex 2 Days Later?

My menstruation started last Dec 19 until Dec 22. I took my first althea pills on the third day of my menstruation (Dec 21). I was not able to follow the instruction that i have to take it on the first day of my bleeding. I had unprotected sex midnight Dec 23. Should i use Emergency contraception like lady pills then continue with my althea pills afterwards? I have been taking althea pills since August.