Thanks for your query at DoctorSpring.com.
Since you had sex within the 72 hour time span after taking the I pill, do not worry. The same pill will protect you against both the acts of intercourse.
There are definite side effects of taking the I pill frequently, and as a substitute for proper contraception.
The I pill would lead to altered withdrawal bleeding / spotting.
It would also interfere with your normal menstrual pattern, and the period could be preponed / delayed.
It is always better to use regular protection / birth control if you are sexually active.
Right now, please do not take another I pill, as it is not necessary, and could lead to more side effects like nausea etc.
All the best.
Please feel free to ask any further follow up questions.