Hey there.
So, based just on what you posted, I don't see that there *is* a problem?
In the case you're thinking something is the matter when someone can (so far, or period) only reach orgasm one very specific way, it's actually very for people to have only a couple -- if that many! -- ways, alone or with partners, that they find they can reach orgasm or ejaculate. I'd say someone very young having only one way is super common. The idea that people can come a million ways isn't at all realistic: porn and other sexual media can make it look that way, but that's not just how it usually is in people's real sexual lives.
Ultimately, doing a bunch of different things should just be about what you both like and want and what feels good for you both. Sometimes sex won't "end" with orgasm for one or both people at all, but if and when people enjoyed themselves with everything they were doing, that's often not even a big deal when it happens.
Do you want to talk about why you think or feel like this is a problem? Is there something else that's an issue with this for you you didn't mention, like you not actually liking being on top, or feeling like you have to do that even when it's not something you want or when you're too tired?