I should do it or not?

That's a very tough decision. In my opinion, maybe you should wait a little more time. I don't know how many time passed since you broke up with your ex-girlfriend, but after a time, she won't mind anymore if you start dating this girl that you liked before. After you wait some time, I definetly think you should try to start a relationship with this girl that you liked before. It looks to me that you like her a long time already and that isn't something easy to find.

Hmm as you have said you have broke up already..before going to this girl you should ascertain that you are still attached to your ex or not..if yes then there's no point in starting a new relationship when you are not over the previous one...if you are completely over the trauma of your breakup and you feel that your previous relationship won't come in a way of your new one then you should definitely approach this new gal..coz may be this relationship is all you have ever dreamt of..so be positive and ask her out. :) all the best:)

You created your own confusion/problem. You already liked the first girl then you should pursue her before committing into a relationship with another girl. Why did you do that, to make the first girl jealous? wrong tactics.

Hmm well if you really love that girl then why not try your luck maybe she likes you too. Does she know you? well bro go and find out if she might give you a chance to date with her and develop the feelings. Good luck..

Ha ha, very confusing. Let me get this straight, you liked a girl before, but got into a relationship with a different girl correct? If so, first of you must consider your relationship with the girl you broke up with first, whether or not you are still good friends. Second you must consider the relationship between the two girls, whether or not they are close friends or just acquainted. Also, in addition to point 1, did you break up in bad terms? To be honest, it should not really matter between the two females. It depends on whether or not you yourself is comfortable dating someone in the same institution, and or if the girl you like is comfortable dating you in the presence of your ex girlfriend. If you are able to, speak with your ex girlfriend and confirm if it is OK, usually they say yes, but focus on her reaction or her smile if she smiles, because usually a fake smile will indicate discomfort. If there is discomfort in general, perhaps you are or will be able to find someone somewhere else. I am sure both females will understand. But good luck.