My girlfriend and I have been in a long-term relationship and believe we are going to marry. She has moved to another city for work, and I have not seen her for over six months. We discussed this before she left and told ourselves that a long-distance relationship would not be a problem but, the longer I stay away from her, the less attached I seem to have become. I have recently begun to have feelings for a colleague and am confused because I am pretty sure she likes me, too. I don’t know if I should break up with my girlfriend. I don’t want to go out with this colleague, but my relationship will be a long-distance one for the foreseeable future and I don’t know if I can continue. What do I do?
If you believe you can’t stay faithful to your girlfriend, you owe it to her as well as yourself to come clean and end this relationship. All long-distance arrangements are hard, but they are not impossible if there is a high level of trust and communication involved, along with a very real desire to want to make it work. Your girlfriend can’t be the only one pulling her weight in this if you are interested in someone else. Ask yourself if this is an infatuation based on your partner’s absence, or if you believe the relationship has run its course. To start something new without ending what you have is cruel and unnecessary, so be honest with yourself before making any decision.

I like this guy a lot but don’t want him to think that I am desperate. Should I ask him out? If I do, he will have the upper hand and may play with my feelings, which is why I am waiting for him to make the right move. He has said nothing so far. 
You’re probably overthinking this. Asking someone out doesn’t automatically give them the upper hand because solid relationships will always be built on equality and mutual respect.