I hate to be the one to say it but if you feel like you aren't getting faster quick enough it could possibly just be age. I am knew to biking but i have alot of experience in training. I was a dancer for 17 years and frankly there was nothing I couldn't do, or get up to speed with, in a short amount of time. Problem is...when you take off an extended period of time it can be increasingly harder to get back into something. The aging process can multiply this fact exponentially. Your body has muscle recognition that kicks in and mentally you feel like you're working hard enough to have been there by now but because your body has aged it will take longer than you expect to actually get there. The upside to this....(yes there is an upside) YOU WILL GET THERE!!!!! If you are doing all the right things, it may take longer but you WILL get there. So just keep on keeping on and it will come. Just don't expect it to be as soon as it used to be.