First of all, I want to remind you of the unpleasant truth: that magic cannot change the laws of physics or biology. If it truly is impossible for you to conceive children, magic will not make it possible. I know a very experienced high priestess whose body was simply unable to conceive naturally, and there was nothing she could do about it, magically or otherwise.
If it is merely *very unlikely or difficult*, there are plenty of old helpers for fertility: wearing charms of acorns or seeds, for example (I'd recommend charging them with their purpose at the full moon). You can also try developing a relationship with a goddess of fertility. Don't just immediately ask her for help: learn about her, get to know her, pray to her, make her offerings. Even gods are more inclined to help the people they're close to, than a complete stranger.
Other than that, the biggest thing I'd suggest is a second medical opinion. See what another doctor has to say about your situation. It's always possible that someone else might have better insight into what might be going on with you. I have a friend who was told she was perimenopausal, and it turned out to be symptoms of a nightshade allergy she didn't know she had. Once she cut the allergy-inducing foods out of her diet, she started having normal periods and was able to conceive. Of course, everyone's story is different (see my comment about the HPS who was not able to conceive naturally: she went on to have a wonderful baby with the help of an egg donor). I wish you luck.