Pressure

You are right that these things take time. It's not uncommon for a sexually inexperienced person not to focus on the needs of their partners. It's with time and experience that many people learn that good sex is about communication, openness and much more about focussing on the person one is with than the technique one uses. Maybe he thinks he is pleasing you, especially if you reassure him and react in all the right ways. Instead of criticising him or pointing out what he isn't doing, suggest to him things that he could do that you would like and enjoy. Spell it out to him. Be conscious of giving plenty of feedback so that he can learn about you and what you like.