I have been a guest reader on CAF for a while. This and similar threads encouraged me to join in to add my two cents. It concerns me that when people ask advice on long-term pregnancy avoidance, the response is often an unqualified recommendation to use NFP. Specifically, I wanted to address an issue that seems overlooked: probabilities of failure compound over time. What does that mean? Say a birth control method gives a 1-in-1000 (0.1%) chance per cycle of becoming pregnant. That sounds quite good. But consider, over about 5 years (60 cycles), this means your probability of becoming pregnant at least once is 6%. Over 10 years, 11%. Not quite so good.
You can search online “what are the real odds that your birth control will fail” and find articles on this. For many forms of birth control (NFP or otherwise), everyone should be clear-eyed about the real risk for failure over long times (and short, too). As the consequences of failure rise, tolerance for risk must drop quickly.
To the original poster: please seek qualified medical professionals to advise you on long-term pregnancy avoidance when a potential pregnancy is high-risk. Given sound medical advice, you can weigh these options and make your decisions with the help of a trusted spiritual advisor. I sympathize with you on the stress this must place on your family life and wish you the best.