Just gave my boyfriend a blowjob for the first time and need a little advice

I know there was just a post about a guy's ideal blowjob but I guess I'm just a bit self-conscious and want to make sure I did it alright. I mean, I think he enjoyed it; he came twice in my mouth and i swallowed and kept going until he was completely done. The main problem is that I have a really bad gag reflex so I couldn't take all that much of him into my mouth. Is there anything I can do to help this? Also, what do I do with the balls? Any advice is much appreciated. Thanks!