Hi, I can’t answer your question specifically, but wanted to congratulate you on being done with chemotherapy! That’s a big hurdle to overcome!
I had a mastectomy (unilateral) with reconstruction with an implant which is quite different from the procedure you are having. I can say after my mastectomy, It was probably 4 weeks before I felt like I could ride again and then still had some muscle soreness.
After my implant reconstruction, it was 3-4 weeks before I could ride, but again, I was still sore for a few weeks after. It’s been not quite 2 years and I don’t have pain anymore, but I still feel it when I lift things or if I am using my pectoral muscles when I ride - it’s an odd feeling. It probably will be different for you with the type of reconstruction you are having.
If you haven’t seen it already, www.breastcancer.org has a good support group forum and there are a few horse people on there who have talked about their experiences. 