Anyone who is in chronic pain will have those days as you describe. It's perfectly normal...it's a grieving process. Yes, it can be quite overwhelming...I honestly know how you feel in that respect. Everyone has this and must come to terms with their illness in their own time. There is no set rules for grief...it's due to the loss of part of our lives. You have nothing whatsoever to feel ashamed for. You didn't ask to become ill, but at some point you will have to come to terms with everything and accept changes in your life. Even when things are grand...the illness will be severe enough some days and we don't feel so grand.
As for coping, we all have our own methods. You must get proper sleep and learn to pace yourself to avoid flare-ups. You must use the word "No" without guilt, because you will find yourself using it more frequently. Limit things like exercise because it can cause a flare...keep it to low impact types. It is also important that you begin treatment for pathogens and boost your immune system. You can find some treatment ideas in our Health Pages. Some members are finding good results from them and it is factual that in over 50% of FMS/CFS patients there are underlying bacterial infections that aren't picked up with typical bloodwork screens. Google "Co-Cure's Good Doctor List" and see if there is a specialist in your area.
As for your relationship, be totally honest with him. He will need to accept that you have an illness which is effecting your CNS (neuro-immune) and until it is recognized and a treatment is made (which treats the problem and not the symptoms) you are going to have days that vary. You will need his understanding and assistance...this is not too much to ask from someone who loves you. Print out a copy of the symptoms of FMS and let him read it so he can better understand what you are experiencing. Having a chronic illness can be taxing on relationships, but empathy and support will go a long ways in helping you get through.
I will keep you in my prayers and hope you feel better soon. It does take time and it is frustrating though. We do understand and will help any way possible.