You're experiencing all this resistance because you don't really want to join a gym.
Oh, sure--you believe you need
to. But that doesn't change the fact that it's drudgery. A chore. One of those grim, no-fun, joyless things you'll have to force yourself to do because you believe you should.
On top of that, you're beating yourself up by deciding that you aren't worthy of love and acceptance until you've changed your physical body. It's not good enough, it's ugly, it's a problem in need of fixing--and the way to fix it is by punishing it.
Small wonder it's so hard to find motivation!
And deep-down you know all this, so you avoid it. Deep-down, you want to enjoy yourself, to have fun, to do things that are pleasurable. Deep-down, you wish you could be comfortable in your current body (while maybe at the same time doing enjoyable things that will help you lose weight and improve your physical condition).
I know once my weight will be reduced I will feel good about me and I will start loving myself.
This is a trap, and I believe this is what you have to change first--not your body, but your thinking
about your body, and the way you feel about it (and, by extension, yourself).
If you can start feeling good about your body right now, as it is, and start loving and accepting yourself right now, the weight issue will eventually resolve itself. Maybe you will find a form of exercise you truly enjoy. Maybe you will be led to discover which foods are right for you. Maybe you won't overeat, or eat junk, out of a sense of dissatisfaction, futility, and frustration because you're happier with yourself and your body as you are.
Your body has its good qualities; focus on them. Be glad for everything that is right about it, and everything that is beautiful--those things do exist. When you catch yourself thinking unkind thoughts toward your body (and thus yourself), stop. Then replace those negative thoughts with something better.
It takes time and patience, because these kinds of harsh, punitive attitudes toward the body are so ingrained, and the messages in advertising, TV, and magazines don't help. But if you can start to feel even a little bit better about your body, and stop treating it as something that must be punished into acceptable form, things will start to change.