Immediately following childbirth is a recuperative time for new mothers. While moms are dealing with a myriad of emotions and "firsts," most first-time mothers have the same concerns.
When can sex resume?
Usually after six weeks of healing (even with a bad tear) your vagina will be ready to receive visitors. Only one, of course—I think that's the understanding. If there were no lacerations or episiotomy, you can even begin sooner, as early as four weeks. Your doctor will "clear" you for sex, as if you're a 747 being cleared for take off. But a GYN exam is not the same thing as sex, in spite of all the overused comments I hear at every high school reunion.
No exam can predict how well you tolerate the rhythmic, persistent mechanical nature of intercourse. It really comes down to your comfort. If sex hurts, back off for another week or two, in spite of what your doctor tells you.
Also, I recommend you not resume until you're "in the mood" again. A baby crying can wreck the mood faster than seeing a mouse run across the bed. And you're tired. And you're worried about the next day. And you're dry. And you haven't used your vagina, except as an exit, for a while.
Stack the deck in your favor by waiting for everything—physical as well as psychological—to be favorable for an enjoyable experience. You may get a pout from your husband, but your body is for both of you, not just him.
Some women complain that they have lost the ability to have an orgasm after delivery. This is probably due to the psychological concerns stated above, but it's also due to the distortion to the anatomy. Almost always it's a temporary problem.
What about birth control?
If you're not breastfeeding, you need not worry about possible exposure of your baby to pharmaceuticals, so you can start immediately. Besides the birth control pill (combination estrogen/progesterone oral contraceptive), the minipill (progesterone only pill), Depoprovera shot, and condoms, there are also the newer Lunelle (estrogen and progesterone injection), and the hard to find Norplant (time released progesterone in under-the-skin capsules).
A diaphragm is a bad idea in the early postpartum period, because it won't fit well after the distorting influences of your recent delivery. Even when you feel you're completely back to normal, you will need to be refitted in case there's been a change in shape of your vagina.
Your doctor won't discuss these options until your final postpartum checkup, and that's OK, because you're not supposed to be having intercourse until cleared anyway.