Second Child...??

Hello...I am new to this board and the forums in general. I am a very happy Mommy to a 2.5 year old son, who my DH and I adopted at his birth. I am a busy Mom with a high energy toddler! I love being a parent and want more children at this time.... However, my hubby says it is a "closed" topic for discussion at this time for him. We went through close to seven years of IF treatments, and then moved to adoption...we are thrilled to be parents, and my husband is a dedicated, loving and committed father who I admire tremendously. I approached him last night about egg donation or embryo adoption as a way to bring a second child in to the world, and he refused to discuss. When I try to talk to him about adopting again, he reminds me of how long our wait was, how emotionally and financially we are drained and that perhaps we are meant to be parents of an only child. I really want my son to have at least one sibling...it is very hard for me to accept the idea of having one child. I am so THANKFUL and feel so blessed by God to have the son that I do..and if God wants me to have only one child, then I know that is His plan...but, I still have this feeling in my heart to add to our family...yet, my hubby does not feel this way. Any ideas of how to approach this subject with him without scaring him off? I would like to try egg donation, but with the tremendous cost of infertility and all the health problems I had associated with IF treatment, I am not sure how I would handle it again. I just want a second child. I love my son so much. I want him to experience the joy and love of a sibling. Thanks in advance for your help!