Hi, we don't use SWIM here.
Using Ketamine specifically as an antidepressant can lead to trouble. It is important to make sure you have exhausted other avenues of possible recovery before going down this road in my opinion. Addiction can easily happen with regular dosing and the temptation to have "just a little bit more" will be constantly present. There are a couple guides on this, but they focus on IM and IV, which is unsustainable for anything more than a short-term solution.
But using drugs while recovering from MDMA isn't the greatest, it does hinder progress but that is more for chronic use of bud or stimulants. I think you'd have more luck with this question in Psychedelic Drugs more than M&ED.