I was 30kg overweight last year and it DID have that effect even on me. Mostly because I knew it'd be a tough hill to climb because girls would label me unfit, unmotivated, etc. It isn't necessarily the weight or the way you look, it is more the attempt to not do anything about it. So I got my booty to the gym and made it evident I was working hard and then the window opened up. Not every girl was like "how you doin" but a few of them did and that gets things started back up.
If it is a legitimate concern, do what you can about it. If it is just because you've always felt this way, then call bullshit on it and don't obsess on your looks. Fix up your inner state of mind so it in itself is sexy. So for example be contagiously fun, or considerate socially, byronic, and that will catch their attention more than your look. You know how you notice a persons relationship to everyone other than you first before judging them? And you automatically assume they are cooler than you? Well that works two ways, one to destroy your self esteem if you believe in it too much, and the other way is to help you build your self esteem by using it to your advantage. You act fun, then others surround you and then others think "hey this guy has IT", and that gets you started. You don't even need others around proofing you, people can tell if people would surround you or not by the vibe you give off.
If this doesn't work, try this weird trick I used to use. I used to try to think of an obscure childrens cartoon episode I haven't thought about in like 20 something years.
Like, I'll search my obscure memory banks for something ludicrous. It creates two effects nostalgia and immediate uncontrollable amusement. Like I'll think of some owl in the koala cartoon, and start laughing my ass off cuz its so fn stupid. A wave of nostalgia washes over me, and then I'm like "hi?!" with a good sense of affability to me.
Worst case scenario where you can't do any of this, don't let it stop you over text, be open and cool in text and you can warm girls up to your "ugly face" online, until they are happy you are doing stuff about it and wanna see you anyway.