Tips to let go my thoughts and orgasm

I love my boyfriend and we had an incredible chemistry, however I’ve only been able to cum once. Even though I’m enjoying all of it, somehow I’m not able to orgasm, I think I’m too much in my head, feeling frustrated cause I’m enjoying and not orgasm that once cancel the other and feel like my worse enemy. He’s doing everything right. Any tips to stop fighting with myself? How can I get out of my head? Breathing exercises?