My Boyfriend Rubbed His Naked Pennis Back N Forth While

My boyfriend rubbed his naked pennis back n forth while I was wearing an underwear but when I went home I saw that my underwear was a little torn and there were 2 or 3 holes but not so big ones. Now Im worried because he was naked and I was just having my underwear and that got torn I don't know how will that lead to preganacy ?