Something to consider is your vitamin B intake. Pregnancy burns up the B vitamins like crazy due to the increased stress on your body. If you are becoming deficient, it can impact your ability to cope well. What you had energy to deal with before will feel more like a crisis now, for example.
Fiber rich foods are brimming over with vitamin B. You can take supplements, but our body best uses vitamin B when it comes together with the fiber source. It is important to get enough vitamin B or you could end up with pre-term labor if deficiencies get dangerously low.
If your eating habits have consistantly been responsible ones, for example, if your life-long eating history has been free of crash dieting, self starvation, other eating disorders, or drug use and if you have been preparing your body for a strong pregnancy by eating lots of dark leafy greens, vegetables, fresh fruits, and other healthy foods and if you have kept to this standard through your pregnancy up until now, then it is likely that your panicky feelings are being caused by something else other than a vitamin B deficiency.
Doctors tend to know little about nutrition, so if you are facing a vitamin deficiency, seeing a nutritionist who specializes in pregnancy nutrition would be great.
Post partum depression tends to hit around the 6th week after delivery. The typical women who gets PPD are those who do not start sleeping through the night by then. Infants generally begin REM sleep by the 6th week, which is also when lochia stops flowing. Up until the 6th week it is beneficial for the baby to nurse at night becuase it helps return the uterus to its pre-pregnant size. After that, it is habit, not necessity. Your baby will benefit from the growth hormone and neurotransmitter repair that only occurs during uninterrupted, deep sleep. So, train your baby with confidence at that point. It might possibly be a difficult step in growth for your baby, but a nurturing response from you will do wonders.
Best of luck to you! There are so many wonderful things to learn about motherhood. It is an intimidating journey, but there are such treasures of wisdom to find!!!