Hi Sumaiyah!
Working out on a slope will definitely take some extra effort, but you should still see improvement. This app should help you keep a better record of your growth, and if you're still not seeing any, don't be afraid to visit your doctor! Let them know that you're trying to get back in shape, but can't gain endurance, or can't maintain your breathing.. it could be something as simple as exercise induced asthma, which is pretty common, and easily managed. It shows up as sudden fatigue and shortness of breath when running.
Let us know how things work out!
Best of luck!
Scott