OP, the main problem is that you are online dating. Most girls prefer a man to be a few inches taller than them, say about head height. With online dating there are plenty of suitors for these girls to choose from, including men that fit the aforementioned preference. They have to weed out the people they talk to and your height is a stumbling block.
If you were to meet these girls in person, they would probably overlook your height, but with online dating they only really have your profile to go off of.
Unfortunately for you, it will be a while before you can meet girls in social spaces.