Am I doing it wrong?

So me and my bf who I’ve know for 2 years now just recently started really getting into the next step by doing sexual things with each other, we haven’t had sex yet but we mess around a lot. He tried eating me out the other day and it felt good but he didn’t finish me and I don’t blame him were both very new at this. So the next time I tried giving him head but I didn’t finish him either although he said it felt good. I need help, how do I know how to make him finish? I try to put my self in positions to make it easier to suck but I get so tired going up and down, am I doing something wrong?