If you can't think of any reasons why a person - man or woman would want to date you, try asking your closet friends to write down (so you've got it to refer to), or tell you in person their favourite qualities about you - why they love you and why they love spending their time with you. Also, ask for them to tell you why the reasons they have given about you are true and why they're sure you'll appeal to others. If you read them every day while you look at yourself in the mirror with a smile on your face, they should give you self-confidence. Also, ask them to write on your list ways that you are naturally such good company.
I advise you to keep them safe for you to go to them on a daily basis, so stick or staple them into your most used note book that you have in an easy to reach place for you - where you spend most of your time, if this is away from your home - keep it in your bag that gets used by you every day.
If you read them out loud to yourself while you're looking at yourself in a mirror - this should help you to feel good about yourself and you should smile with happiness because you're you.
Reading it out loud gets your brain to pay more attention to what you are saying by retraining it to feel and believe - plus if you read it 10 times every day, you're brain should remember the kind words you've said to yourself.
The10 times repeating something to yourself is a medically proven fact that this works - so if you have exams coming up, this would be a very useful skill - pattern of behaviour to use, to help you pass your exam, and possibly get the highest grades or marks out of everyone else you has taken the same test or had the same exam as you. When you achieve your goals and you read them to yourself on a daily basis, this should help you to believe in yourself - this should raise your confidence level. If a person puts you down - read the positive things about you in your note pad until you can smile again, because you know you can succeed at all things you put your efforts and mind into.