I was gaining weight, so I have been doing many different types of exercises.

Every time I would end up exhausted and looked for another sport, so I would end up gaining back the weight I had lost.

The same thing had happened again and again, until I totally gave up the ideal perfect body.

Then, one day, someone recommended I try swimming.

Swimming was not included in my sports' list; I was too shy to wear a swimsuit.

(If I had known the water in a pool was actually shoulder-high, I would have tried three years ago.)

Anyway, I decided to try swimming and now is my favorite exercise.

Since I was gaining weight, I have been doing many kinds of exercises. [Alternative: "getting heavy" is another phrase for "gaining weight".]

These are quite interesting and helpful for losing weight, but too hard for me to last for a long time. [Alternative: "...too hard for me to keep doing for long."]

Everytime I got exhausted and looked for other sports, I gained weight back.

The same thing had happened again and again, until I totally gave up on having a perfect body.

Then, one day, someone recommended swimming.

Swimming was never included in my list of sports; I was too shy to wear a swimsuit.

(If I had known the water in a pool comes up to my shoulder, I would have tried three years ago.) [Alternative: "the water... is shoulder deep"]

Anyway, I decided to give it a try and now swimming is my favorite sport. ["it" refers to "swimming"; you can also say "one of my favorite sports", but if you like it better than any other sport, "my favorite sport" is correct]

Every time I got exhausted and looked for another sport (or: type of exercise), I gained weight back (or: regained the weight that I had lost).

The same thing had happened again and again, until I totally gave up on having the perfect body.

(If I had known the water in a pool was actually my shoulder height (or: shoulder deep), I would have tried three years ago.)

Since I've been gaining was getting weight, I have been doing many different types kinds of exercises.

Playing squash, badminton, tennis and table tennis, doing dance sports, going to a fitness club, hiking, and so on....

These are quite interesting and helpful ways for losing weight but, they're too hard for me to last do for a long time.

Every time I became exhausted and went looking for another sports, I would gain the weight back.

The same thing had happened again and again, until I totally gave up on having the perfect body.

Then, one day, someone recommended a swimming.

(If I had known the water in the a pool was actually my up to my shoulder's-high, I would have tried three years ago.)

Anyway, I decided to give it a try and now swimming is my favorite sports.

These days, I swim with flippers fins.