Its only too late when you say it is. As you have seen with other posters in this thread, you are not the only person who is in their early 20's and has had no romantic history. The best thing for you to do is to identify what are the main causes of your current status; are there things you do to prevent potential relationships on purpose? Do you have mannerisms and social skills that others would deem awkward? Are you just shy? Are you busy with other things that consume your time?
I was 18 before I had any romantic encounter, but even out of the blue it DOES happen. 20 is still plenty young, I should know.

Good luck OP.