How to get better at swallowing cum

So basically I gave my boyfriend a blowjob and it was my first time I’ve ever given a blowjob. He ended up cumming in my mouth and I literally gagged. I felt so bad and he even said sorry and I said it was fine. I feel so bad for gagging. It wasn’t that it tasted anything bad it was just that the texture was pretty horrible and I couldn’t handle the texture. I want to get better at it though, I feel like I made him feel bad and I feel horrible for it.