What are my chances of being pregnant?!?

Hi! So on Saturday my boyfriend asked me to just touch his penis to my vagina and I agreed. There was no penetration involved but I instantly started to freak out about getting pregnant. He said he had previously masturbated that morning but wiped off after and then took a shower. I know that pre-ejaculation can happen when men are excited and that it can sometimes have sperm in it. Just after he did that I looked down and I saw some sticky stuff on the side of the tip (it sort of looked like a clear slime) but I'm unsure if that was from me or him. Anyways, my main question is what are the chances of me becoming pregnant? And are the chances high or is it something that I shouldn't stress that much over?  I am having very bad anxiety over this, but I am aware that stress can make your period come late some I am trying not to think about it.