It sounds like you have suffered a lot of loss over the past few years. I can understand how the illness and fear of losing your gerbil friends is hard. I know another pet will not be able to replace them but perhaps having the company of a new friend may ease your pain and help to bring some joy into your life during this hard time.
You have a big heart to have such love for those small animals, it is not everyday someone cares so much for another living thing. You are a good person, I wish you all the best.