condom came off How concerned should we be?

Before we realized I had finished and the condom had come off in her (tried a few new positions) we use spermicidal condoms, she is due to start her period this week. How concerned should we be with getting an emergency contraceptive? We both are in our 20s, try to always be safe, but this happened. Not exactly sure when the condom came off, if she tightened up and as I pulled it removed, but it was in her, she had to remove it, and tried to remove any residue left. With the use of the Spermicidal condom I am unsure of our chances and with her being due any day to start I did not have any clue. Should we go get an EC today? This happened just last night, less then 12 hours ago. Thanks for any responses.