as other have said , you are not too old to adopt an older child ( school age). if you are a mixed heritage family you might also be considered for a toddler. However, adoption of older children is very risky as a large proportion of placements break down. But there are many children needing a family
can i ask how long you and your Dh have been together? how does he feel about adopting rather than having another bio child? does he have a good relationship with his children?
neither are you too old to conceive. i conceived twice straight away at 41. the first pregnanacy ended in early miscarriage ( very common) and the second in DS1. then i had DSS at 43, also conceived very easily. i had healthy pregnancies and babies 
if you surf mumsnet you will find there are many other women having babies in their 40s. i think there were 27, 000 babies born last year in the UK to women in their 40s
the statistics are confused by teh fact that many women of 41 have been TTC for years. if you have not tried yet then your chances are much better
i knwo you have issues about pg and childbirth, but i suspect that SS will want you to have had conselling for these anyway BEFORE you start the adoption process. they are often reluctant to start assessing families without fertility problems who have chosen not to have bio children. this is because these families very often drop out
also adopting a child might bring up soem of these issues for you, as you will be becoming a mother by another route
so i woudl advise you to get some counselling / therapy for these now, while you beging to explore all your options