How to leave the man you love with all your heart

So my boyfriend is telling me to have sex with other men but don’t tell him when I’ve done it, I tried to have sex with him but he just shoved me away, he lies to me telling me he was at a friends who I’ve never heard of, he comes home late, he’s 20 years older than me, I love him more than anything but I feel like he don’t love me anymore, do I stay or do I leave, even when I do leave I go straight back to him