Lack of confidence affect most of us from time to time at various levels. If you feel ready to take a relationship to the next level you just have to take a deep breath and try to move it on.
You seem coy on exactly how far you have got with the existing relationship and where you wish to go next, but, you say you are already dating, why not try a small kiss at the end of the evening and see what the reaction is ?
Ultimately you have to push doubts away for a bit and simply play act the person you want to be until you know it you had progressed where you wanted to be, or have learnt that this one wasn't going there anyway and you need to search elsewhere for love. Risking a bit of embarassment is well worth the potential prize, as it may change your life.