Hi, Emily, and welcome! You have already gotten some great responses from our members. We have all been there. I think the stress and worry you are having is causing even more pain. You are projecting yourself in the future and thinking you can't handle it. Please don't do that. You know you have fibro now so now you have to face it head on and get it under control. You can't just accept the diagnosis and not do anything to help yourself. I'm so glad you came here because we can tell you ways to help yourself and have a full and enjoyable life in spite of this illness.
What muscle relaxer are you taking? I was just given a muscle relaxer that I actually had used 20+ years before. It's called Robaxin. Whenever I started up the Robaxin, the first pill would put me right to sleep. But any pills after that didn't and I felt/feel just fine! I was given these again several months ago and this will be on a long-term basis. I have absolutely no side effects...except I got more sleep with the first pill. 
You might try your muscle relaxer again. Choose a weekend that your hubby will be home. The first pill will most likely put you to sleep so take it right before bedtime. Then try a second pill as prescribed by your doctor. See what happens. It might take a couple of doses for your body to get used to it but your husband can step in if it continues to make you sleepy. If you find you can't take the medication, talk to your doctor. See if you can try Robaxin instead. We are all so different so I can't say definitely that Robaxin wouldn't bother you but it's been on the market a very long time so it must be good. This med has given me significant relief from pain I was experiencing.
I also take a few supplements that have helped me a lot. I use malic acid/magnesium supplements, vitamin D3 supplements, and an alternative product called Curamin that has won awards for pain relief. I also use ibuprofen with food and extra strength Tylenol. I do stretching exercises, walk daily, and pace myself when doing things. Do a little, rest, do a little more, rest, etc. It all gets done but in a different time frame.
Moist heat helps a lot. A hot shower will lessen the pain and make you more flexible. Some have a Bed Buddy. You can find these at Walgreen's, Bed, Bath & Beyond and other places. You put them in the microwave and they give off moist heat and feel soooo good!
Fibro fog is a cognitive memory problem. We can do some of the craziest things! When it first hit me, I thought I had Alzheimer's and was quite distressed. Then I realized what it was and relaxed with it. I write everything down and do memory games to help me remember things. I laugh at the dumb things I do instead of getting upset because I found by getting upset, my memory was worse! But when I relaxed with it, I couldn remember things better. If I can't come up with a word, my friends and family finish the sentence and I thank them with a smile on my face. After all, that's not the end of the world.
Last week I boiled up a week's worth of hard boiled eggs. I put them in a bowl and put the bowl back in the cupboard instead of the refrigerator! My daughter and I had a good laugh over that. I've tried to start my car with the key to my freezer and of course forget what I was going to get at the store or even in a room in my home. I even forgot my telephone number and had to get out my checkbook and read it off my checks! But don't let that get you down. If you relax, laugh at the mistakes, I just bet it will get a little better for you. Here is a cute site that will show you that you are not alone.
http://webspace.webring.com/people/fc/cfsdays/follies.htm
Your children are so young. Try to remember that when they do things that can cause you pain. They don't understand. Just let them know that hurts Mommy and they will try to be more careful. You are not a bad mother. You are a mother that has health problems. My children were 4, 2, and 1 years old when I was hit with Crohn's disease. I had to use the bathroom about 25 times a day. I was chained to the bathroom and I couldn't even take my children on a picnic because of it. BUT I made good use of the time with my children and they knew I was there for them and home, too. Also, I developed fibromyalgia shortly after that. I was a mess! LOL They are all adults now and a few years ago I started talking about their childhood and how badly I felt that I couldn't do the things with them that I would have if I had been healthy. I started to cry and they were shocked! They said they had a wonderful childhood. I was a wonderful mother and there to help them. I always had a home-cooked meal on the table, was there when they needed help, advice, etc. They said I was a far better mother than all the rest of their friends. See, it's the time you spend with your children that counts. Just being there, loving them, is all they really want. So don't worry about being a bad mother. I just know you aren't because this has been a cause of worry for you. Stop worrying and enjoy those little children!
Be sure to read Fibro 101...the first thread on the forum. There are links to good info about fibro and you will learn a lot there. There are links to some of the supplements that I mentioned and how they work in your body too. So do read it. You just might see yourself there.
I hope some of this has helped you and has given you some ideas. Don't hesitate to ask questions because we are here to help you. Hope to hear more from you soon.
Sherrine