Spoilers: for a lot of us, that "I can't draw well enough" feeling never goes away. It's always there, nagging at us. In fact, I just woke up two hours before my alarm and spend the whole time staring at the ceiling angsting about how I'm not good enough at drawing environments.
If it's getting in the way of you getting anything done, I think you need to take a moment and try to figure out WHAT it is you feel you're lacking. Really look at your work, and look at the work of artists who inspire you, and figure out what it is that you want to achieve. Do you want to improve your anatomy skills? Do you want to get better at colour-theory? Is it environments you want to do better, or something else? Pick a target, and spend some time focusing on improving that.
Say that what you want is to get a lot better at drawing hands. Sit down with your sketchbook, or with your tablet (the skills are transferable), and draw a bunch of hands. Draw 100 hands. By the end of it you'll be better at hands by sheer force of repetition. The same thing goes for any other art-skill you want to have. You learn by doing, but you need to figure out what it is you WANT to do - and we can't really help you with that bit. You need to look at your own work and really think about what you want to achieve.
This is a separate issue that we also can't solve for you; this is an issue between you and your family/friends. I'm sorry we can't help with this particular thing.
Pro-tip? If you keep putting off a comic until you're "good enough", you're never going to make it. Seriously - just do the thing. It doesn't matter if your art-skills aren't brilliant, or if you screw something up along the way; you learn more by doing it than you do by preparing for it.
