Yes ! cloth. As sperms are microscopic.Dont take chances.
Next Steps
wait till 25 day of cycle ando a serum Bhcg to see if it is positive. Also depends on which day of her cycle you ejaculated. if close to her ovulatime .
Health Tips
Always be careful .. even without penetration semen deposited at the vulval opening pregnancy can happen as sperm is microscopic and travels from the vagina .