Then you will be back complaining about butt pain, hand numbness, neck pain, back pain. Ride your current bike until you get fitter... and be patient about it. It takes time. Do it little by little, not all at once. I used to ride hybrids a lot when riding with the kids, even though I'm a road bike guy. I think you are imagining improvements from riding a road bike that will not be there. All you need to do right now is to set up your hybrid for more efficient riding. If your handlbars are high, find a way to lower them just enough that you are leaning forward when pedaling. If you have a riser bar, swap it for a flat bar and put bar ends on it. That will get you most of what a drop bar can do for you, and it will be more than enough for most riding. Ensure that your saddle is set up not too low, and at a neutral position of knee-over-pedal (you have to start somewhere). And then, ride. To gain fitness, you have to ride often, and long enough, but it doesn't have to be 50 miles. Even just 10-15 miles is plenty if you do it at least every other day or so (say, 4-5 times a week).