Polyamory

Hi everyone, I’m new to this website and polyamory; only a year in. I love the idea of polyamory, and I’ve been enjoying it, but these past couple of months I can’t wrap my head around my partner (male) having sex with his other partner (female). Thinking of it gives me so much anxiety. It makes me feel sick knowing that they are getting intimate, having sex, sleeping naked together, etc. Any tips to self-regulate these thoughts into compersion instead?