I need all the help i can get!

My husband and I tried to conceive and we were successful, however, we went our separate ways for a few weeks and I had a slip up. I told my husband this when I told him I was pregnant and he was okay with this, but now his family is demanding a paternity test. I used this app to get pregnant. I conceived in October 2014, my cycle was the 5th-9th and I ovulated the 16th-22nd. I didn't have my slip up until after the 25th. Does anyone have any suggestions on who they think the father is?