It depends...what kind of benefits do you have at that job? Will it cover maternity leave, etc? It would be easier to find a job now before adding the stress of another baby, but for me it would depend on what benefits were available at my new job. If benefits were no object I'd say find a new job NOW. Why be miserable for another year? It's not likely to get better and it will be stressful dealing with that, taking care of your family and being pregnant on top of it.
It's a tough decision,
Suzanne