I don’t think you need a challenge right now.
There is a time and a place for a challenge workout, or a training plan that has you purposefully overreaching. They are best reserved for when life stress is low. Your life stress isn’t low. You can’t kill yourself in every avenue of your life and have something left at the end.
Gaining weight is good for you, continue gaining weight. That being said, continue if you can without finding other ways to engage in self-harm. I understand this is uncomfortable for you, and sometimes it is acceptable to create ourselves a plateau before we continue to progress if we aren’t sure we can maintain our current progress without suffering through a period of regression. Perhaps this will be a strained metaphor, but, sometimes when there isn’t any wind in the sails the best thing a ship can do is to not sink when it isn’t possible to move forward.
From your earlier posts with regards to college, it is very clear that you have an elevated need for control. I didn’t reply at the time I do believe, and I just wanted to add a supporting voice to all of the people that pointed out that part of higher education is learning how to deal with things not running smoothly. For me, my first experience of the sort, was during high-school during a project-course where the teacher went in purposefully and deleted the entire project from the school’s servers to see if us students could adapt and restore things from our own hard-drives etcetera. Anyway, I digress. My intent with bringing this up, your need for control, is that you’ll never be in control. Life will always throw you a curve-ball, or several, at a time. It’s best to find a way to live where you can have an idea of what you want to do but remain adaptive to reality.
Many eating disorders start when someone’s life is tumultuous because usually one thing we can control is our food intake. But this tends to only work for a while, as eventually the body will start fighting us. And now we feel bereft of all control, which furthers our distress. So we tighten up our reins even further, perpetuating the negative feedback loop.
I should add that from my recent readings on eating disorders it would appear that being chronically underfed has as a side-effect obsessive thought-patterns and a malformed body-image (I’ve mentioned the latter previously). The former explains how we can perhaps rationally understand that what we are doing is disadvantageous to us but make it really hard to escape our “habits”. It might also be by this token why, when someone exits a diet, they struggle mentally.
I’m probably over-stepping my boundaries, but I prefer to associate my thinking with tangible examples. @jskrabac, obviously very successful with his physique endevours, had this thread,
and in other threads he is forever a voice of reason, but he struggled a bit with his carb intake, thinking that he was getting fat. But he kept his carb intake up, and after a while his body found a new balance and seemingly whatever demons were plaguing his mind with regards to gaining body fat they disappeared,
And it is funny that, because I was the one that suggested it yet I get caught up in the same traps myself. I can rationally tangibly associate actionable dietary habits with “science” but that doesn’t stop my brain from getting caught in the bottom of a maelstrom if I’ve been under-feeding myself. Whether or not what I’ve read about under-feeding encouraging this faulty thinking is accurate or not I do not know, but it does align very well with what I’ve observed in myself and others.
It is believed that the reason this happens is actually to save energy, that it’s metabolically cheaper for the brain to continue along in already established thought-patterns.
That’s skin, not fatty tissue.
Anyway, to return a bit to weight gain here’s a thought that I originally learned about when it came to losing weight but it also applies in reverse.
Let’s hypothesise that a person needs to lose 10kg to get to the level of leanness they want to.
But if they were in a maintenance/hypertrophy period to begin with, they are presumably carrying as much glycogen as they can (which binds water, 4g of water per gram of glycogen), and they are probably as hydrated as they’ll get and their bowels are “full”. So, they are carrying some 2-3 kilos maybe (250-270g of glycogen → 1kg of water + bowel weight) “extra” that’ll also leave their body as they lose those ten kilos of fat.
And, for every kilogram of fat that leaves the body, they are going to lose some other stuff to go along with that. There are fat-soluble minerals stored in fatty tissue, there’s some water there, and maybe one would even lose some muscle. I recall reading that barring muscle loss you are looking at losing 250 grams of other stuff per every kilo of fat.
This would apply in reverse too, and then as we are gaining both muscle and fat you are picking up weight on two fronts. New muscle mass means even greater glycogen stores, so not only does the muscles add scale weight but also the glycogen and the water. And so forth, you are smart enough that I don’t have to write it all out.
What we can try and do though, when gaining muscle, is to not beat it into smithereens so we actually end up gaining some muscle. I.e., you train, you trigger a hypertrophy response through mTor-signalling then we don’t want to do a ton of cardio which would break down the already damaged muscle further meaning that whatever recovery it manages to undergo it doesn’t end up being a net loss nor do we want to signal AMPK which would inhibit the mTor-response. This entire paragraph was written to encourage you to walk a lot less 
@jskrabac if you dislike me using you as an example let me know and I’ll remove it