I understand your situation completely. I am a guy, however I've been rejected by several girls in various ways. I know it hurts.
Understand that in life nothing is for sure. What i mean is, you can't guarantee success in anything. The best we can do is put ourselves in the best position to achieve our goals.
Did you know for sure that you would be accepted to your uni? Probably not. When you graduate from your uni will your first job interview be a success? Unlikely.
We cannot guarantee a outcome to a situation, However we can put ourselves in the best position to achieve it and give ourselves the best chance. Put another way, a guy will never ask you out 100% of the time, but you can increase that percentage.
How do you do this you may ask? Well for one thing its the environment. If your looking for the more serious relationship/ less physical/sexual generally you would want to ask out guys that you meet in a serious setting like a uni, organized event, etc. If you want a more sexual/ physical thing parties, pubs and clubs are probably better. Obviously this is not 100% true.
Getting to know the guy before making a move can also make the relationship more emotional and less sexual. Also just try to improve your appearance with exercise, nice clothes, and put a smile on your face.
Lastly life can be just as much fun single. Believe it or not some people want to be single again. The grass isn't always greener. Less freedom, free time, and less hanging out with your friends are all negative consequences.
Now go out there and live your life how you want to! Don't let fear of rejection cripple you any longer. Ask them out but move on if it doesn't work out!