Oh yes, the letdown or after effect of all the craziness. All the fear and anxiety about the surgery, the relief of getting back to normal and feeling more normal again, can feel like depression, or just wading through quicksand, teary and easily emotional. You have been on a such a roller coaster for a while now and it's just stopped and returned to the station. You are likely just letting down your guard because everything is okay and now the emotions that stayed under the surface are coming up. Honor your body for the journey it has taken and survived, honor your self for being so resilient and steadfast, pamper yourself and do all the little things that feel cherishing like extra sleep, foot baths with spa treatment, comfy clothes and cheerful movies, music that makes you feel good, books that make you think. Anything that feels good, and just give it time and know that it will ease once you've felt the feelings and let them go.
If it lasts more than 2 weeks or gets worse, or severe, please contact your team and let them know, they will likely have resources for you, in fact, no reason to wait if your team has a psychologist you feel comfortable with, go ahead and talk to them. It would likely be very helpful.
Take care.