I have ocd. no-penetration sex on 12th jan, had period as expected on 31st, had next normal period 28 feb. still can't stop worrying about pregnancy.

You aren't pregnant: It is highly unusual to get pregnant with non vaginal penetration sex (i'm presuming that the penis and sperm were just outside the vaginal opening). If the sperm is more than a few inches away from the vagina it's impossible to get pregnant. Since you have had 2 normal periods at the usual time then you are not pregnant. If you want, do a pregnancy test to reassure yourself.