TTC (trying to cum) for 10 months

I've been with my boyfriend since september and have been very sexual since then. We finally had sex in December. He's way more experienced than me and very great in bed, but this whole time I could not cum. He's great, dirty, dominant and makes me feel great but I've managed a few times to get close but never actually orgasmed with him. I've masturbated for ages and can make myself cum so easily and I've shown him how I do it but it just doesn't happen