I feel so defeated

I hate feeling this way. Tired. Useless. Defeated. Doing anything takes every ounce of motivation I have. Theres literally no reason for it. I was fine a couple weeks ago. Nothing happened, nothing changed. It just gets harder and harder to do things, to work, to take care of myself. Then I feel guilty because the people around me have to deal with me. I wonder if my kids notice- which, they're older now, so I know they do. Feeling that more awful knowing I'm such a crappy parent, and pissed off and more depressed because I dont want to do anything and just lay on the couch sleeping on and off while he plays video games. I was in such a good place less than a month ago. I was content, I had some confidence, I was able to work and make some good money consistently. I even filed to get more time with my son. Then these last couple weeks I can feel myself sliding down into the darkness of depression again. Can I really handle more time with my son? Can I really handle all of the parent duties, or is he better off with his Dad? Maybe I will just stick with my every other weekend instead of going for mostly equal time. it's such a defeating feeling. Feeling yourself give up more and more each day cause it's just too f-ing hard to get up and shower and be a productive person. I hate it. I dont know how to over come it, and I fear I'm just going to drowned in this depression.