I'm so, so sorry for your loss.
I've been working with the LOA for about 4 years, and have used it to gradually change my life and the dynamic of my family. My very favorite book on the subject is Ask and it is Given by Esther and Jerry Hicks. The first half of the this book is basic info on LOA, and the content is h is available in many other places as well. It is the second half of this book that is the real gem. It has 22 different processes (or activities or exercises) that help you shift your vibration, and therefore your point of attraction. Some of them are journaling exercises.
We manifest things our feelings, not with our words, and since your fundemental feeling right now is desperation, you will continue to manifest more desperation until you figure out a way to shift that. In your situation, overwhelming sadness and grief are completely understandable. According to the book, rather than trying to move all the way up to joy, which is just a much bigger shift that you can realistically make, the goal is simply to move up very slightly on the emotional scale, but to make it a real shift. Rather than attempting to fake something that you don't really feel, move to a slightly more positive emotion that you really can feel.
I'm not sure which of the processes in the book would be most helpful for you, or I would type it up. I would recommend getting this book and reading through it to figure that out. (most large bookstores keep it in stock in the new age section).
The ironic thing about working with LOA in this way is that once we really clear our vibration, what ever it was that the thought we needed to be happy/have peace/be complete is less important, because we found the happiness/peace/completeness without it. I know that even entertaining that idea is threatening because you very deeply believe that you MUST have another baby to be happy and feel complete.
Sometimes I've manifested the *reason* for what I wanted without manifesting the thing I thought I needed to have that. For example, when I first started this, I was morbidly obese and got winded walking up a flight of stairs. I wanted to be slender and healthy, and one of the reasons I wanted that was so that I could enjoy shopping for clothes. (there were a bunch of other reasons as well). I manifested being able to enjoy shopping for clothes long before I lost all the weight I needed to. I didn't have to be as slender as I thought I needed to be in order to have that. (That was a stepping stone to where I wanted to be -- I'm now healthy, fit, curvy and a yoga teacher).
Sometimes I've manifest the core of what I really wanted, but in a very, very different form that I could have imagined it. For example, when I started this, we were homeschooling and I wanted some things to be different about that. A lot of stuff happened, and now my kids attend an AMAZING alternative school which has every thing for them that I wanted to be true about homeschooling but never was. At times, it was really painfully getting to this point because my belief about what I wanted was out of step with the best way for that to happen.
My advice would be to start by journaling about why you want a baby, what it is that you think a baby will give you.
Also, and this isn't really about LOA, I think that you and your DH are on very different waves lengths and aren't currently unable to hear each other. I'm wondering if marriage counseling to help you both process this loss and move forward would be helpful. You haven't shared anything about the actual story here, but I'm wondering if what happened was traumatic for both of you, but that you guys are processing in very different ways, and that difference is driving you further away from each other. I'm wondering if his need to keep you safe and your desire to have another child are such at odds, that without both of you really making peace with what happened and truly being able empathize with each other, the gulf will continue to deepen over time. I think that a neutral professional could be very helpful.