From my personal expereince I say yes this is a detox.
I stress from my personal expereince.
I haven't been using MMS very long, and I found exactly what you stated. About pain in the right breast and for me a bit of swelling. For me also, I have had this rash for years under my arm, (next to my breast) my doctor repeated states its a heat rash, I have long suspected it is a yeast infection, and have tried many things to no avail.
On the advice of Pam in another thread, (I had written I was nausea, she advice to reduce the amount I was taking), I reduced the amount of MMS I was taking, I was way over doing it and the pain has subsided, and I am detoxing.
I was taking 5 activated drops a day and I was nausea all the time, I have had to reduce to 2 activated drops a days for no or very slightly nausea, and next week will increase by another drop.
Below may sound gross or offend some, I am sorry if that is the case.
How do I know I am detoxing?
Pee in a bucket during the day, keep all of your pee from the day in that bucket, (with a lid/cover), do not add toilet paper.
I found three things from this:
1. Your pee is a great indicator of detoxing
2. If your pee smell is strong your detoxing (I've had members of the family comment on the smell after using just the toilet and flushing), so this gave me the idea to try to measure "status" and "improvement" over time.
3. By the end of the day, there was this really gross thick film on the pee, definitely detoxing.
Rinse bucket, really well, add a few drops of javex, and start over the next day. Or use once week, which I will start to do now that I have a good sense of what is coming out.
I have been using MMS maybe, maybe, I can't find my book, right now, maybe a month.
Hope this helps.