Not unusual. It is not unusual to have decreased sensation after child birth, but it should be temporary. Trauma to the birth canal can be partly responsible. The stress of having to raise a child can also mentally affect the quality of your sexual experience. If the problem does not resolve, then call your doctor.
YES. GET TESTED. When you are about ready to give birth you have a huge amount of extra fluid. When you lose that quickly at birth, the brain area that controls testosterone and other hormones can be stunned. These should be tested 10 days after birth: dht, free testosterone, freet3 [active thyroid] and others. Women need e2 or estradiol, Progesterone and Dht or testosterone for optimal orgasms. At 31 some drop.