Firstly, I'd work on your self-esteem before attempting to date, because thinking lowly of yourself could have you accepting bullies and predators. Those types of people look for people just like you--someone who they think they can control, bully, manipulate, etc.
Whatever it takes--therapy, reading books on how to boost your self-love, do it. And don't date until you can think, "I'm the treasure, and any guy will be lucky enough to have me, because I'm a wonderful person and will be a great partner."
It's always good, of course, to feel confident by playing up your best traits, and have a haircut and clothes that suit you. Just because you're not your own cup of tea looks wise doesn't mean a particular man will feel the same. He might find you to have a beautiful smile with a charming personality.
And just because if a second date didn't happen because he chooses not to, doesn't mean you're lacking in any way. I, myself, have found some men to be attractive and pleasant, yet the chemistry is missing for me. That's biology. Yes, it's upsetting when you'd like to see a guy again and he doesn't, but you need better self-talk, like, "Well, that's disappointing. Next!"
After my first marriage ended, I had to go on dates with about 30 men for several years before I met a keeper. Sometimes the guy wasn't into me. Sometimes I wasn't into the guy. Sometimes neither of us felt the chemistry. Because love is magical so it's not going to happen every time you have a first meet with a guy, or it could fizzle out quickly. So you should practice resiliency instead of feeling down about yourself. It's called being realistic and knowing that you usually have to dig through a lot of sand to find the treasure.
I suggest you presently make a dealbreaker list and a must-have list and stick to it. Gain a sense of power that you have standards and you're in the driver seat when it comes to who is worthy of being in your life and who you need to make a quick exit from. I also suggest not keeping all your eggs in one basket with OLD. There are Meetup.com groups, volunteer work, classes in cooking, dance, gardening, art. Make a goal of putting yourself out into the world for leisure and fun activities a few times a week. Good luck and let us know how it goes.