I have a few tips that might be helpful to you...
I personally don't think that you should make too much of an effort to contact your exes or try to remember your ex-girlfriends. Even if it was good, it might put you in the spot where you might be like "why am I not at that same point right now?"
However, DO do the following things:
1) Listen to things that will get you in a good mood. Dance, techno, hip-hop, jazz music are all good suggestions. Stay away from the love songs, just listen to something upbeat that gets you in the mood! Just dance!
2) Turn on some comedy tapes! Comedy will always put you in a better mood than you are now! Laughing will get those endorphins out and have you enjoying yourself. If you know all your comedy by heart, go out and get some new stuff that you think you will like (sometimes comedy loses its value if its heard too many times in a small time period)
3) Talk to one of your friends that can make you laugh or is usually in a good mood. Just talk about whatever you want. Sports, current events, stupid sh*t that made you laugh you both have done recently..talk to someone who is really outgoing and can put you in a good mood easily.
4) If it's a nice day, go for a walk. Take a shower, dress nice, put on some nice cologne, brush your teeth and get them nice and clean, just be impeccable for the moment. And then go outside... I guarantee you that girls will be checking you out, and it doesn't matter if they're hot or not. Don't even approach if you don't want to..just soak up the sunshine, smile and keep walking!
5) Work out.. Working out can definitely get you in a good mood.. Every one of us has one aspect that they truly love about themselves.. some of us have great bodies.. others have strong facial features.. (My strong feature is my face... whenever I've just taken a shower and my hair and face are still wet, I just gel my hair up, blow dry it to look like I want, and then just check myself out in the mirror! It know it sounds kind of vain, but hey..it makes me feel good!). If you have a good body, just flex in the mirror... again..sometimes vanity is a GOOD thing!
6) Set up a table with all your accomplishments. Test scores, awards, medals, trophies, look through pictures that you took with hot girls, look through all the stuff your exes bought you, relive the great times you had with your family and friends.. Soak it all in.. crazy things that you did with your friends (remember the time you got wasted with your friends and started taking pictures of girls asses just for the hell of it and you just didn't give a sh*t?, etc.) Bask in the moment because you were the one who made all of it special!
Man, life is a cycle. But the faster you ride it, the closer you will be to those sweet confident times again!