Thank you for the additional information. It helps.
It sounds like your husband (and you) are dealing with an anxiety disorder. Anxiety is a very common disorder that millions of people deal with every day. At any given time, you will find that at least 1 out of every 5 people in a clinic or ER are there for an anxiety related issue.
Your husband's response to his anxiety by manifesting it through a physical ailment or disease is a very common reaction. A lot of anxiety sufferers think there is something physically wrong with them and many develop an extreme fear of death.
Since he will not go for treatment right now, I will list some resources and ideas here for him and you to consider to get him started on helping himself.
One, if he does ever consider going to therapy, he should know that anxiety is very highly treatable. Most people experience a great reduction in symptoms and are able to cope better with life after treatment. Treatment can be short term, so don't think of therapy as a long, drawn out event before relief is found. Cognative Behavioral therapy (CBT) is the most common and effective therapy. Integrated therapy is a new therapy that is also very effective. You can seek out a therapist by asking your doctor for a referral or if you attend church, your pastor can help. Also, you can search on line at http://therapists.psychologytoday.com/rms/.
Two, there are many self help options he can try at home. One excellent book is called The Anxiety and Phobia Workbook by Edmund Bourne. Another option is the books and programs by Lucinda Bassett. Check out your local library and Amazon.com under anxiety and phobias to find many options for self help.
Three, have your husband talk with a pastor, if he attends church. Reassurance and faith often greatly help those who suffer with anxiety about their health and death.
Four, consider taking a break yourself. Caring for two young children and helping your husband with anxiety can be enormously draining. Do you have someone who can stay with the kids for an hour or two? Go out and do something for yourself. See a movie, browse a bookstore, shop anything that would help the stress. When the kids go to bed at night, plan a quiet dinner. Watch a movie. Take a bath. Whatever helps you relax and cope. You can also consider going to therapy yourself to help you have someone to talk to. It also gives your husband a chance to see how it helps you and maybe he would be more willing to go.
Five, he may want to consider on line self help groups. Here is a link to get him started:
Please let me know if you have any further questions I can help you with.
I hope this helped,