Hi thanks for your question.
Your chances of getting pregnant are very,very less,as for getting pregnant sperms sholud reach cervical canal which is not possible with finger and secondly you took morning after pill.So no chance of pregnancy
. Relax and enjoy.Headache and fullness in uterus
may be due to next due periods which may be very near or due to tension of getting pregnant.For light headache you can take mild analgesic
Hope this answers your question.