How to conquer anxiety (for reals)

So I have what I like to call sexual anxiety. Now, for all the ladies out there that are going to encourage me to take a sex ed class or read a book (true story), I just wanna say that I am fully aware of how getting pregnant works. I never said my concerns are rational and valid, nevertheless, they continue to persevere and make making out with my boyfriend an experience of sheer fear that somehow something awful will happen and somehow his sperm cells will find their way into my vagina (even though we’re both wearing underwear) and the 1 in a 1,000,000,000 chance of my getting pregnant from this will happen. It’s stupid. Sooooo stupid. I’m 20 and this is my first actual relationship where it’s progressively gotten physical. Any CONSTRUCTIVE (emphasis on that word right there) for how to silence these thoughts and enjoy myself?