Advice from someone more experienced

Hello everyone

Me and my partner have a great sex life and are pretty compatible in our bed. While we are very lucky, I have an issue and I would like your advice.

My partner really enjoys when I hit her cervix and this helps her orgasm easily. Our go to position is cowgirl where she can position herself to hit it and I can also grab her pelvis and guide her myself. While I really enjoy it, I miss being on top. I have been awfuly inconsistent hitting her cervix like that. The only position that has worked consistently is prone bone with a sex pillow but this becomes too intense for her and we have to stop after a while. Every other position we have tried is very inconsistent, with me hitting it way less.

I don't know if this is a skill issue or me not being long enough to reach it. I really wish I could be on top and give her the pleasure she gets from riding me or to take control of things and let her rest a bit while keep pleasing her the way she likes it. She has managed to finish with penetration before but it is way harder and rarer than when I rub her cervix.

Do you have any advice for me?

If it's a skill issue, how could I improve? I know that I need to be more fit and not get tired as easily so I can explore her body better.

If it's a penile length issue, how could I make the deep penetration positions work for me?

I hope the post isn't too crude. Thank you all.