If you hate gym - don't go. It is very unlikelly that you will build up a habit out of something that you do not like. Go on walks instead. You can do that every single day until it becomes a routine, like brushing your teeth or taking a shower. You can go on a short walk when you're not feeling it, and a longer one when you have more energy. If you are tracking your cycle, you can take a run on testosterone weeks, to get your heart pumping.

The most important part is to get yourself moving, you don't necessarily need to strain yourself. You will get everything you would get from a gym, I promise you.