1.) You are worth the time. This is not a matter how much attention you get. You are ALWAYS worth the time - and you would be, even if you stopped drawing tomorrow and never drew another line for the rest of your life.
2.) I don't know how many regular readers you have, but it seems to be a trend that most of us have a handful of regular commenters, and a LOT of silent ones. I have nearly 1500 readers - I have maybe 10-15 who comment regularly. That's a LOT of silent readers.
So don't let the number of responses lead you to think that people don't care. They just might not think it's all that important to comment on the stuff they read.
3.) Whether or not people comment depends on a lot of things - whether your comic leaves them asking questions, whether or not you open up in the author's notes beneath the comic, whether you're active on the forums or not, or simply whether or not they feel like it that day. It's not something you can control, and not something you should be measuring your popularity on.
4.) I know that posting stuff and getting no response feels terrible - it's like shouting in an empty room, and hearing nothing back but your own voice. It sucks and its discouraging - but we all deal with that in one way or another. A webcomic audience is something that builds slowly, over the course of years, and slow and steady really does win the race.
Count every response, however small, as tiny victory. Carry that tiny victory along with you, and know that that is good enough - you reached out, and someone reached back! Awesome! Now keep going, because you've got their attention!
5.) Do you have any friends online who also make webcomics? Like, do you have a Twitter account, perhaps, and are you following other webcomic creators there? I've found that it makes a LOT of difference to surround yourself with other people who also draw and/or make comics. Their attention and appreciation for your work will be genuine and serious, since they know what it's like to create as well.
6.) It sounds as though the stress is getting to you. It is perhaps a good idea to take a step back, take a deep breath, and really assess what it is that's making you feel bad and then deal with that. Is it something else going on in your life, or is it just the comic? Do you have underlying issues of self-worth that have nothing to do with the comic, but are now messing with you because of the lack of responses? Etc., etc.