Could I be pregnant after becoming 40 years old. Also I have fibromalgia. Could it be worse.?

Yes. Yes it is possible to become pregnant after 40. Interestingly, when women with fibromyalgia become pregnant they commonly experience decreased intensity of their symptoms while they are pregnant. The reason for this is unclear. My theory is that the release of hormones during pregnancy, especially Relaxin, ameliorates chronic spasm of soft tissue such as muscle and myofascia. .
Sure. Many women are delaying pregnancy until older but should plan for it with your ob. You may have varying amounts of pain with fibromyalgia as it has no known cause by definition and pregnancy can normally have aches and pains. Problem will be how you will deal with pain while pregnant.
You can get pregnant. Unless you have had a hysterectomy or have gone through premature menopause you can certainly get pregnant, having normal menstrual cycles. No published stdies have looked at females with fibromyalgia during pregnancy, but the high levels of hormones do import slight euphoria!