If you talk to your son about support group have you ever thought of framing it as him coming there with you to help support you? Since he's living at home (?), you can tell him how important it would be to have you go there and give you the extra strength because you'd like to share the experience with him? Maybe if you frame the question in a positive light, and it doesn't seem like you're trying to force him into it, it could benefit both of you?

Maybe start seeing a therapist too? If you hold onto worries they'll make you start to feel ill. if you can talk to a therapist about ways to relax the mind, the body, it may help with the worrying. Worrying is a bad addiction that wants to stay and make your life miserable. Learning to take your life back from those thoughts, and to live in the present is an important skill to acquire. It doesn't mean that the worrying thoughts go away, but it means you can deal with them. If you talk to a therapist, the could give you those tools to help you. If you talk to the pdoc, and tell them the meds aren't working they can try and change things.

Also, don't feel at fault. People with bipolar who take care of themselves can be as high functioning as any other adult. My dad is probably dx untreated bp, and he has a treated bp daughter but I don't blame him because I have the diagnosis. I love my dad so why would I blame him for something as trivial as that? Talk to your son about it. I am sure he loves his mom. :')