I dont feel old!

My husband is the best man ever. We agreed to not try, but not prevent pregnancy. That leaves me feeling less stressed than if i were throwing every ounce of energy into ttc. I am 43 and he is 42. I have a 10 year old from a previous relationship and we have a 4 year old together. Since i was 33 and 39 when i had my children, I wonder what my chances are? I don't feel my age and i am very healthy. Both my children were conceived naturally. I am not telling anyone that i would like another baby. I don't think anyone would criticize to my face, but i guess i view it as a private matter and i don't want to answer nagging questions.