If you are dealing with anxiety and depression that you have never dealt with before the problems in your marriage started happening, you are very likely dealing with what is known as "event based" issues, versus the true long term "personal based" problems that occur within people due to actual mental health issues...
The questions you are asking about how you feel are really quite normal, in fact I asked a psychologist last week:
"I have never felt anything like this, am I going insane?" because I honestly believed I was losing my mind, the ups and downs and differences in mood swings, and how I could feel one way about the relationship and another way 2 minutes later.
The psychologist actually laughed, not at me or anything, but wanted me to feel more at ease I believe, and replied:
"What you are going through is a NORMAL reaction to an insane situation, any rational typical spouse who loves their significant other will experience very typical feelings to what you are going through."
I continue to go back to this, whether I'm suddenly on cloud 9 (which is rare) or if I've completely broken down and end up on the phone with my father in tears (thankfully also rare, but more common than the cloud 9 feelings right now unfortunately).
Do your best to take care of yourself right now, and realize that even as I type this, I am not very good at taking my own advice. I am watching my wife self destruct, she "plans" to move out in a week, I use "plans" very loosely because she has done next to nothing to actually plan anything, she just continues to say that she is moving out March 1st despite a near total lack of activity on her part to prepare for it, in the meantime my heart screams for her not to go and my head says "dude, it's been two years, you have to let her go if you ever expect to move on yourself".
I believe the longer you attempt to fix a relationship in which the other person does not work on it themselves, the more damage you do to yourself, the more you "lose yourself" within the process. That is what I am trying to come back from right now. I don't know if any of this helps you, or others, I hope so. One thing is for sure, in my position I take care of 60+ Soldiers, and this entire horrible situation will give me invaluable advice to give any of them who goes through this in the future.
The sheer volume of divorces that happen is utterly staggering, and shows how morally irresponsible this entire planet is at this time, this isn't a religious viewpoint, just an observation, because no one should ever treat another person the way that a lot of spouses do, in terms of destroying what really are good marriages for absurd reasons. I'm not talking about the truly abusive or infidelity filled marriages in which one partner has finally said "enough", I'm talking about actual good loving relationships where a spouse does something truly stupid/ignorant and ends up destroying everything their loving partner ever believed in.