I cannot get to the Big O

So my SO and I are new to the sex life, our first time was in March but since the summer has started and we are home from college we have had A LOT of sex. The sex is good and he is amazing. He is the guy I am planning to have children with one day but I can never get to that point. I hate it and it's so fustrating because I want to and I think it is making him feel like he is not good enough. I do not know what to do, please if anyone has any tips for me please share with me.... I'm desperate 😞😞