ttc for the 12 time

hi all I am 36 with 11 amazing children. My husband and i have been ttc for three months nows. I get stupidly upset each month. Am I to old to be having more kids or am I just over thinking about get pregnant. I love all my children and husband so much I know there is so much more love i have to give to another little bundle of joy. i have an undersctive thyroid as well. I am so upset with my self right. please no negatively please help with positive fixes x