Yes, it makes complete sense to me....these things just happen, without warning and sometimes for no apparent reason whatsoever, and there's not a whole lot that can be done about it, besides seeking therapy, taking meds if it gets to the point where you need them to function properly, somewhat like myself, and just trying to deal with it the best you can. I totally hear where you're coming from with the sleeping issues. I myself have sleeping issues, on and off. Sometimes I'll sleep fine, and it will be all good, until one day, BAM, it hits me, I can't sleep or I'm not tired enough to sleep, and so then my whole pattern is out of wack for a while afterwards.
I would suggest seeing a doctor, even if it's just a regular physician, and talking about the feelings you've been having lately, because it cannot hurt at all to get things off your chest....if anything, it will help, trust me. The physician can most likely direct you to a good place to go to get some help. As far as the feeling of guilt and sadness, that's normal with depression, even when there's no relevant reason to be depressed, like I said, it just happens sometimes...happens to the best of us! I actually haven't cried a single tear in a long time, mainly due to the fact that a lot of days, all I feel is numb or blank, even if I am severely depressed, anxious, etc. I usually don't have any tears waiting to come out. I can understand though, and it's normal, and also it's healthy and good for you to cry sometimes, it really is, so don't be too worried about that.
The main thing for you to do right now, would be to talk to someone about your feelings and try to pinpoint what the problem is and/or what can be done about it to help you. I wish you the best of luck, and hang in there. I always try to look at it like this: "It can always be worse, I'm thankful for what I have and I will do whatever it takes to make tomorrow a better day, and if it isn't, there's always the next day."
Hope to hear how things are going, and take it easy.