Hello, and I hope I can help you today.
It takes at least 6 weeks for a c-section wound to heal completely with the staples in place... With a wound separation it can take longer. The fact that you needed a drain under your skin means there was blood under the skin when they stapled the incision closed which can interfere with
wound healing. The other reason you feel pain on that side is that most of the time, the knots of the stitches under the skin are tied on the right side.
Things you can do to help the right side heal is to shower every day with the dressing off, using soap and water around the open area and letting the soapy water rinse over the wound, rinse it well, and then pat it gently dry with a clean towel. Apply a clean gauze or any clean absorbent material (maxi pads work for this too, just tuck them under your belly in your underwear) to cover the incision and keep it clean. Do not apply any creams to the area.
Most of the time the gap will close after 6-8 weeks. I suggest you make an appointment to see your doctor for 6 weeks after the birth if you do not have one already for re-evaluation. If you notice a bad small coming from the wound, or green discharge (small blood or yellow is normal) or if the pain is getting worse, see your doctor sooner. I am sure the incision will heal, it just needs more time.
I hope this adequately answers your question and that my advice was helpful. Best wishes, Dr. Brown