I am new to this site, so we haven't had the pleasure of "meeting" directly, but I have read a lot of your posts and you give a lot of support to everyone, now it is your turn!
I know when I was working, I too almost never called in sick for myself - I would call in sick if one of my kids was sick, but rarely for myself. If I did, I felt like I was letting the pain rule my life, like the pain was "winning" somehow. Eventually, it was getting harder and harder to get there everyday, and when I got home, I couldn't do anything else.
I, too, fell into a terrible depression and wound up having a nervous breakdown because I was pushing myself too hard and I couldn't come to terms with how much pain I was in and how much that pain was affecting every aspect of my life. I still have trouble to this day dealing with my limitations. My mind may be willing, but my body is not!!! After my breakdown happened, when I looked back, I realized I had been spiraling downward for several weeks, but I was too busy trying to "do it all" to realize what was happening to me.
I still push myself to do as much as I possibly can, I try to ask for help when I need it, but there are definitely times when my husband will tell me that I am overdoing it and if I don't take care of myself, it will always catch up with me and I will wind up in bed for several days, and ocassionally I land myself in the hospital for a few days to get the pain back under control.
I'm sorry to go on about myself, I just wanted to tell you from experience, that you do need to take care of yourself! The housework isn't going anywhere and the people you work with need to learn to stand on there own two feet because you are only human and there will be times (like with your upcoming surgery) where you will not be able to "do it all" for a period of time.
Please let go of the guilt, relax, and resolve it in your mind that you are doing what you have to do so that you will be able to cope with tomorrow.