Dude it's like there's no pressure on you to improve. You want things to be a certain way, but you have this crippling fear. We've all had it, it sucks. A lot of guys have an external, social pressure from their friends that makes them improve with girls. None of us have that, so we need to create an internal pressure.
It is your responsibility to WANT to get better. We can tell you how, and motivate you somewhat, but this one is really on you. Decide what you want, and get it.
(To explain push/pull: The basic concept is you want what you can't have. So you need to give someone space, but also be able to make strong, decisive moves. An example is this girl that I texted last night. I hooked up with her almost a year ago when she came to visit my friend. She'll be coming back next month. The reason we still talk very sexually, with a strong spark, is twofold. One, we haven't had sex yet, so there's something to look forward to. And second, I barely talk to her. I contact her maybe 40% of the time, and we always have conversations when I do. She contacts me 60% and I rarely respond to her. Last night I teased her, she responds with "jeeeze, dont be so mean" so I say "

love you. Come here" and she says "I want your weiner in me." I thought at first that it was sarcastic, who says weiner? but apparently it wasn't. The push/pull in this is alternating gaps of no reply, with sexual conversations. Also the teasing alternated with sexual, sweeter talk. The first time we hooked up she called me mean often.)
^push/pull is a great concept, but at this stage you're far more likely to notice it working when you're doing well with a girl than if you tried to plan it out. This girls your girlfriend, you don't need tricks.