Is it obligatory for me to be content with my current children and abandon the idea of conceiving again, especially with my husband's insistence on that, and the resulting psychological and health pressures?

The Sharia has encouraged having many children. The default is that each spouse has the right to procreate, and neither may prevent the other except with their permission. It is permissible to delay childbearing for a clear benefit, such as the well-being of a sick woman, but it is not permissible out of fear of poverty or the difficulties of raising children. If there is a clear excuse for the woman where pregnancy would cause her obvious harm, as certified by trustworthy doctors, then she is permitted to prevent pregnancy through a permissible method.