Several of my friends have had babies after turning 40. Each of these additions were planned.
One friend has MS too. She had been married unhappily for many years to an abusive man. Her sons were teens when she was finally able to leave him and get a divorce. She married a man who had not had any children. They decided to try. She was able to have another son then a daughter. She is nearly 60 now and her younger children are 11 and 13. Her older sons have their own children.
One mom and dad joined the LDS church after having their sons. They decided to increase the size of their family and had 2 more children. She was in her 40's and her son's were in their teens.
One of my friends had her 7th child a few years ago, she was in her early 40's. Her oldest daughter was pregnant at the same time. She gave her parents their 40th grandchild. The daughter gave her mom and dad their first grandchild a month later.
Many many many people have children in their 40's and some even in their 50's. It is not all that uncommon anymore.
If you want another child then have another child. It is not that big of a deal. If it would make you feel any better then make an appointment to talk to the doc.
I think large families are wonderful and wish I could have had more children. But later in life. I sucked as a parent with my daughter. I do better now with my grand kids.