Dear S.,
I'm sorry about your miscarriage and I understand the fear of having another one. You should get to a really good OB for a thorough check up which may help alleviate some of those fears.
Now, as far as spacing your children....
In my life, I have only known two couples who said "We're going to get pregnant one year after the wedding and then again 18 months after the baby is born" (or whatever their specific plan was) and it actually happened that way. We can plan for things, but when it comes to getting pregnant or our babies doing things based on a preconceived time schedule, more often than not, that planning goes right out the window.
I don't think you should worry so much about what other people are doing or when they are having their kids. All things are different for all families. These things have a way of working themselves out just the way they are supposed to.
I was told I would never have children so I was very happy to get my daughter and only now and then did I wish I could have another baby because I loved and enjoyed her so much, it would have been nice to double it. But, I was thankful for my little blessing. I did have a miscarriage after that. My husband and I never used birth control and I never got pregnant so it wasn't something I thought a whole lot about. Then to my surprise, years later, guess what. I had a baby boy.
I certainly never would have planned my children just shy of 10 years apart, but looking back, I wouldn't have done it differently even if I could have. There were absolutely no jealousy issues, no competing for my attention and my daughter LOVED her little brother. She was such a big help and loved dressing him, playing with him and reading to him. He was HER baby! It really couldn't have worked out any better. God knew what he was doing. I will say it was tough on my son when his sister was old enough to move out on her own, but they are still very close. They call each other all the time and she comes and gets him to spend the day together, takes him shopping and out to lunch. She's taken him to concerts and things a sibling closer in age wouldn't be able to do. Surprising enough, my daughter has several friends her age with little brothers my son's age so they all go do things together.
My kids have each other and adore each other. The space in their ages is just part of their lives. They don't know any different.
So, my advise is to relax. Don't feel left behind if you aren't having kids at the same time other people do. Heck, Michell Duggar is on baby #19 so when you think of it that way, it's easier to put things in perspective, I think.
Something I often tell myself is, Lord, let me appreciate the wait as well as the answer.
Meaning, enjoy your 3 year old and your husband and know that even if it takes two years to have another baby, you will be filled with joy and say the same thing I did...
"I wouldn't have changed a thing".
Many blessings to you!