My girlfriend’s sexual past makes me anxious and irrational

I really love her and want to be with her, but I live in constant fear of being cheated onMy girlfriend has a very colourful sexual past, having been in at least three threesomes. This, coupled with the fact that she travels for her work and most of her friends are male, puts me in constant fear of being cheated on (having been cheated on in the past). And this drives me to have irrational reactions and outbursts. I really love this girl and I have no doubt about wanting to be with her, but I ca