šŸ§˜ When I meditate using the breath as my anchor, I start controlling how I breathe. How can I stop doing this?

You're definitely not alone in finding that you sometimes control the breath during your practice. This is really common. Often, as soon as we hear the instruction to breathe "naturally" we change the way we breathe! The instruction here is really just to be with the breath however it is, from moment to moment. So in one sense, even if you're manipulating the breath in some way, that's how the breath is in that moment, so you can simply bring your awareness to what is happening. Bringing curiosity to the experience can also be helpful, as it allows us to be open to the breath however it is, whether shallow, tight, uncomfortable, etc.

If you continue having a hard time using the breath as the focus of your meditation, another possibility is to shift the focus to either sound or overall body sensations. When you work with sound as your primary focus, you simply direct the attention to all the ambient sounds in your environment. There is no need to try to hear anything or to identify what it is you are hearing; just allow any sounds that arise in your environment to be known.

If you work with the overall sensations of the body as the primary focus of your practice, you allow the awareness to rest on the experience of what the body sensations are as you are sitting. Notice the feeling of the whole body sitting, see if you can feel into any points of contact between your body and the chair or cushion you are sitting on and allow those sensations to be known. 

With either of these two options the practice would be the same as it is when you use the breath as the primary focus. Every time you notice that the mind has gotten caught in thought, gently bring the attention back to either sounds or the body sensations (whichever you have chosen as your primary focus). It is generally best to choose a primary focus at the start of a meditation session and to stick with it throughout the session.